Science Lab Tech Lects Part 1 2024-2025 PDF

Science Laboratory Technology (SLT) Part (1) Delgado Community College's Science and Math Division offers an Associate of Applied Science degree in Science Laboratory Technology (SLT). The Science Laboratory Technology Program provides students with the nece...

Science Laboratory Technology (SLT) Part (1) Delgado Community College's Science and Math Division offers an Associate of Applied Science degree in Science Laboratory Technology (SLT). The Science Laboratory Technology Program provides students with the necessary skills and techniques for standard, everyday science laboratory work. Science Laboratory Technology Program focuses on the fundamental principles of the biological and physical sciences and emphasizes analytical laboratory techniques and applications, specifically in chemistry and biology. The curriculum enables the student to explore a variety of laboratory testing techniques and to prepare and operate various types of tools and electronic analysis equipment. The Science Laboratory Technology Program prepares graduates for employment in biological and associated science laboratories. The science laboratory technology fields of opportunity include biological, agricultural, chemical and food science, environmental science and prevention, forensic, forest and conservation, geological, and energy technology. This program focuses on biological and chemical concentrations with laboratory experiences that cover a variety of applications in biological, biochemical, chemical, water, environmental, forensic, petrochemical, and agricultural science areas. Is science and laboratory technology? Science Laboratory Technology Program focuses on the fundamental principles of the biological and physical sciences and emphasizes analytical laboratory techniques and applications, specifically in the realms of chemistry and biology. What is science and laboratory technology? Science Laboratory Technology Program focuses on the fundamental principles of the biological and physical sciences and emphasizes analytical laboratory techniques and applications, specifically in the realms of chemistry and biology.  SCIENCE LABORATORY TECHNOLOGY In a scientific investigation, there is an attitude that demands of one to explore his environment or the unknown, develop the relevant hypothesis in order to establish its acceptability or otherwise. This type of investigation can only be carried out in a laboratory.  What is Science Laboratory?  The science Laboratory is a setting or place to try out specific scientific information and test principles and theories in science. It is thus a place or room where scientific experiments are carried out. It is appropriately equipped with various items that are required in the urge to provide answers to intriguing questions in science. Overview of Science Laboratory Technology The programme Science Laboratory Technology is designed to produce Technicians/Technologists capable of carrying out various Laboratory analysts and practical work under minimal supervision. Goals and Objectives of Science Laboratory Technology They are involved in a variety of laboratory based investigation within biological, chemical, physical and life scientific areas where they; 1. Assist in chemical analysis in laboratories in educational institutions, food and chemical industries, research institutes etc. 2. Assist in biological experiments and investigations in industrial and institutional laboratories, farms, museums and other nature establishments. 3. Assist in physics experiments in institutions and industries 4. Supervise Laboratories in educational institutions. 5. Assist in organization and management of scientific warehouse. 6. Assist in marketing and distribution of scientific equipment and consumables. Microbiological Science Field The science laboratory technology fields of opportunity include chemical, biological, agricultural and food science, environmental science and prevention, forensic, forest and conservation, geological, and energy technology. Laboratory A laboratory is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physicians' offices, clinics, hospitals, and regional and national referral centers. Overview The organization and contents of laboratories are determined by the differing requirements of the specialists working within. A physics laboratory might contain a particle accelerator or vacuum chamber, while a metallurgy laboratory could have apparatus for casting or refining metals or for testing their strength. A chemist or biologist might use a wet laboratory, while a psychologist's laboratory might be a room with one-way mirrors and hidden cameras in which to observe behavior. In some laboratories, such as those commonly used by computer scientists, computers (sometimes supercomputers) are used for either simulations or the analysis of data. Scientists in other fields will still use other types of laboratories. Engineers use laboratories as well to design, build, and test technological devices. Scientific laboratories can be found as research room and learning spaces in schools and universities, industry, government, or military facilities, and even aboard ships and spacecraft. Despite the underlying notion of the lab as a confined space for experts, the term "laboratory" is also increasingly applied to workshop spaces such as Living Labs, Fab Labs, or Hackerspaces, in which people meet to work on societal problems or make prototypes, working collaboratively or sharing resources. This development is inspired by new, participatory approaches to science and innovation and relies on user-centred design methods and concepts like Open innovation or User innovation. One distinctive feature of work in Open Labs is the phenomenon of translation, driven by the different backgrounds and levels of expertise of the people involved. Techniques Laboratory techniques are the set of procedures used on natural sciences such as chemistry, biology, physics to conduct an experiment, all of them follow the scientific method; while some of them involve the use of complex laboratory equipment from laboratory glassware to electrical devices, and others require more specific or expensive supplies. Equipment and supplies Laboratory equipment refers to the various tools and equipment used by scientists working in a laboratory: The classical equipment includes tools such as Bunsen burners and microscopes as well as specialty equipment such as operant conditioning chambers, spectrophotometers and calorimeters. Molecular biology laboratories + Life science laboratories  laboratory glassware such as the beaker or reagent bottle  Autoclave  Microscope  Centrifuges  Shakers & mixers  Pipette  Analytical devices as HPLC or spectrophotometers  Thermal cyclers (PCR)  Photometer  Refrigerators and Freezers  Universal testing machine  ULT Freezers  Incubators  Bioreactor  Biological safety cabinets  Sequencing instruments  Fume hoods  Environmental chamber  Humidifier  Weighing scale  Reagents (supply)  Pipettes tips (supply)  Polymer (supply) consumables for small volumes (µL and mL scale), mainly sterile Laboratory equipment is generally used to either perform an experiment or to take measurements and gather data. Larger or more sophisticated equipment is generally called a scientific instrument. Safety Laboratory safety In many laboratories, hazards are present. Laboratory hazards might include poisons; infectious agents; flammable, explosive, or radioactive materials; moving machinery; extreme temperatures; lasers, strong magnetic fields or high voltage. Therefore, safety precautions are vitally important. Rules exist to minimize the individual's risk, and safety equipment is used to protect the lab users from injury or to assist in responding to an emergency. The Occupational Safety and Health Administration (OSHA) in the United States, recognizing the unique characteristics of the laboratory workplace, has tailored a standard for occupational exposure to hazardous chemicals in laboratories. This standard is often referred to as the "Laboratory Standard". Under this standard, a laboratory is required to produce a Chemical Hygiene Plan (CHP) which addresses the specific hazards found in its location, and its approach to them. In determining the proper Chemical Hygiene Plan (CHP) for a particular business or laboratory, it is necessary to understand the requirements of the standard, evaluation of the current safety, health and environmental practices and assessment of the hazards. The CHP must be reviewed annually. Many schools and businesses employ safety, health, and environmental specialists, such as a Chemical Hygiene Officer (CHO) to develop, manage, and evaluate their CHP. Inspections and audits like also be conducted on a regular basis to assess hazards due to chemical handling and storage, electrical equipment, biohazards, hazardous waste management, chemical waste, housekeeping, radiation safety and emergency preparedness, ventilation as well as respiratory testing and indoor air quality. An important element of such audits is the review of regulatory compliance and the training of individuals who have access to or work in the laboratory. Training is critical to the ongoing safe operation of the laboratory facility. Educators, staff and management must be engaged in working to reduce the likelihood of accidents, injuries and potential litigation. Efforts are made to ensure laboratory safety videos are both relevant and engaging. Sustainability The effects of climate change are becoming more dire and mitigation strategies are needed even for the research community. While many laboratories are used to perform research to find innovative solutions to this global challenge, sustainable working practices in the labs are also contributing factors towards a greener environment. Many labs are already trying to minimize their environmental impact by reducing energy consumption, recycling, and implementing waste sorting processes to ensure correct disposal. Fume hoods Presumably the major contributor to this high energy consumption are fume hoods. Significant impact can be achieved by keeping the opening height as low as possible when working and keeping them closed when not in use. One possibility to help with this, could be to install automatic systems, which close the hoods after an inactivity period of a certain length and turn off the lights as well. So the flow can be regulated better and is not unnecessarily kept at a very high level. Freezers Normally, freezers are kept at −80 °C. One such device can consume up to the same amount of energy as a single-family household (25 kWh/day). Increasing the temperature to −70 °C makes it possible to use 40% less energy and still keep most of your samples safely stored. Air condensers Minimizing the consumption of water can be achieved by changing from water- cooled condensers to air-cooled condensers, which take advantage of the large surface area to cool. Laboratory electronics The use of ovens is very helpful to dry glassware, but those installations can consume a lot of energy. Employing timers to regulate their use during nights and weekends, can reduce their impact on energy consumption enormously. Waste sorting and disposal The disposal of chemically/biologically contaminated waste requires a lot of energy. Regular waste however requires much less energy or can even be recycled to some degree. Not every object in a lab is contaminated, but often ends up in the contaminated waste, driving up energy costs for waste disposal. A good sorting and recycling system for non-contaminated lab waste will allow lab users to act sustainably and correctly dispose of waste. Organization Organization of laboratories is an area of focus in sociology. Scientists consider how their work should be organized, which could be based on themes, teams, projects or fields of expertise. Work is divided, not only between different jobs of the laboratory such as the researchers, engineers and technicians, but also in terms of autonomy (should the work be individual or in groups). For example, one research group has a schedule where they conduct research on their own topic of interest for one day of the week, but for the rest they work on a given group project. Finance management is yet another organizational issue. There are three main factors that contribute to the organizational form of a laboratory:  The educational background of the researchers and their socialization process.  The intellectual process involved in their work, including the type of investigation and equipment they use.  The laboratory's history.  Weighing scale Set of balance scales, with weights Weighing scale for a baby includes a ruler for height measurement A scale or balance is a device used to measure weight or mass. These are also known as mass scales, weight scales, mass balances, and weight balances. The traditional scale consists of two plates or bowls suspended at equal distances from a fulcrum. One plate holds an object of unknown mass (or weight), while known masses are added to the other plate until static equilibrium is achieved and the plates level off, which happens when the masses on the two plates are equal. The perfect scale rests at neutral. A spring scale will make use of a spring of known stiffness to determine mass (or weight). Suspending a certain mass will extend the spring by a certain amount depending on the spring's stiffness (or spring constant). The heavier the object, the more the spring stretches, as described in Hooke's law. Other types of scales making use of different physical principles also exist. Some scales can be calibrated to read in units of force (weight) such as newtons instead of units of mass such as kilograms. Scales and balances are widely used in commerce, as many products are sold and packaged by mass. Pan balance History The Ancient Egyptian Book of the Dead depicts a scene in which a scribe's heart is weighed against the feather of truth. The balance scale is such a simple device that its usage likely far predates the evidence. What has allowed archaeologists to link artifacts to weighing scales are the stones for determining absolute mass. The balance scale itself was probably used to determine relative mass long before absolute mass. The oldest attested evidence for the existence of weighing scales dates to the Fourth Dynasty of Egypt, with Deben (unit) balance weights, from the reign of Sneferu (c. 2600 BC) excavated, though earlier usage has been proposed. Carved stones bearing marks denoting mass and the Egyptian hieroglyphic symbol for gold have been discovered, which suggests that Egyptian merchants had been using an established system of mass measurement to catalog gold shipments or gold mine yields. Although no actual scales from this era have survived, many sets of weighing stones as well as murals depicting the use of balance scales suggest widespread usage. Examples, dating c. 2400–1800 BC, have also been found in the Indus River valley. Uniform, polished stone cubes discovered in early settlements were probably used as mass-setting stones in balance scales. Although the cubes bear no markings, their masses are multiples of a common denominator. The cubes are made of many different kinds of stones with varying densities. Clearly their mass, not their size or other characteristics, was a factor in sculpting these cubes. In China, the earliest weighing balance excavated was from a tomb of the State of Chu of the Chinese Warring States Period dating back to the 3rd to 4th century BC in Mount Zuojiagong near Changsha, Hunan. The balance was made of wood and used bronze masses. Variations on the balance scale, including devices like the cheap and inaccurate bismar (unequal-armed scales), began to see common usage by c. 400 B.C. by many small merchants and their customers. A plethora of scale varieties each boasting advantages and improvements over one another appear throughout recorded history, with such great inventors as Leonardo da Vinci lending a personal hand in their development. Even with all the advances in weighing scale design and development, all scales until the seventeenth century AD were variations on the balance scale. The standardization of the weights used – and ensuring traders used the correct weights – was a considerable preoccupation of governments throughout this time.  Weighing dishes from the island of Thera, Minoan civilization, 2000–1500 BC Assyrian lion weights (8th century BC) in the British Museum Finely crafted pan balance or scales, with boxed set of standardized gram masses The original form of a balance consisted of a beam with a fulcrum at its center. For highest accuracy, the fulcrum would consist of a sharp V-shaped pivot seated in a shallower V-shaped bearing. To determine the mass of the object, a combination of reference masses was hung on one end of the beam while the object of unknown mass was hung on the other end. For high precision work, such as empirical chemistry, the center beam balance is still one of the most accurate technologies available, and is commonly used for calibrating test masses. However, bronze fragments discovered in central Germany and Italy had been used during the Bronze Age as an early form of currency. In the same time period, merchants had used standard weights of equivalent value between 8 and 10.5 grams from Great Britain to Mesopotamia. Mechanical balances The balance was the first mass measuring instrument invented. In its traditional form, it consists of a pivoted horizontal lever with arms of equal length – the beam – and a weighing pan suspended from each arm (hence the plural name "scales" for a weighing instrument). The unknown mass is placed in one pan and standard masses are added to the other pan until the beam is as close to equilibrium as possible. In precision balances, a more accurate determination of the mass is given by the position of a sliding mass moved along a graduated scale. Technically, a balance compares weight rather than mass, but, in a given gravitational field (such as Earth's gravity), the weight of an object is proportional to its mass, so the standard masses used with balances are usually labeled in units of mass (e.g. g or kg). Two 10-decagram masses Market hawker weighing meat (in catty) on a beam balance, Malaysia (1969) Masses of 50, 20, 1, 2, 5 and 10 grams Aluminum, mass-produced balance scale (steelyard balance) sold and used throughout China: the scale can be inverted and held by the larger ring beneath the user's right hand to produce greater leverage for heavier loads (Hainan, China, 2011) To reduce the need for large reference masses, an off-center beam can be used. A balance with an off-center beam can be almost as accurate as a scale with a center beam, but the off-center beam requires special reference masses and cannot be intrinsically checked for accuracy by simply swapping the contents of the pans as a center-beam balance can. To reduce the need for small graduated reference masses, a sliding weight called a poise can be installed so that it can be positioned along a calibrated scale. A poise adds further intricacies to the calibration procedure, since the exact mass of the poise must be adjusted to the exact lever ratio of the beam. For greater convenience in placing large and awkward loads, a platform can be floated on a cantilever beam system which brings the proportional force to a noseiron bearing; this pulls on a stilyard rod to transmit the reduced force to a conveniently sized beam. One still sees this design in portable beam balances of 500 kg capacity which are commonly used in harsh environments without electricity, as well as in the lighter duty mechanical bathroom scale (which actually uses a spring scale, internally). The additional pivots and bearings all reduce the accuracy and complicate calibration; the float system must be corrected for corner errors before the span is corrected by adjusting the balance beam and poise. Further developments have included a "gear balance" in which the parallelogram is replaced by any odd number of interlocking gears greater than one, with alternating gears of the same size and with the central gear fixed to a stand and the outside gears fixed to pans, as well as the "sprocket gear balance" consisting of a bicycle-type chain looped around an odd number of sprockets with the central one fixed and the outermost two free to pivot and attached to a pan. Because it has more moving joints which add friction, the Roberval balance is consistently less accurate than the traditional beam balance, but for many purposes this is compensated for by its usability. Torsion balance scale made by Torbal Torsion balance The torsion balance is one of the most mechanically accurate and analog balances. Pharmacy schools still teach how to use torsion balances in the U.S. It utilizes pans like a traditional balance that lie on top of a mechanical chamber which bases measurements on the amount of twisting of a wire or fiber inside the chamber. The scale must still use a calibration weight to compare against, and can weigh objects greater than 120 mg and come within a margin of error +/- 7 mg. Many microbalances and ultra-microbalances that weigh fractional gram values are torsion balances. A common fiber type is quartz crystal. Microbalance A microbalance (also called an ultramicrobalance, or nanobalance) is an instrument capable of making precise measurements of the mass of objects of relatively small mass: on the order of a million parts of a gram and below. Analytical balance Weighing balance, with precision of 0.1 mg An analytical balance is a class of balance designed to measure small mass in the sub-milligram range. The measuring pan of an analytical balance (0.1 mg or better) is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield. The use of a mechanically vented balance safety enclosure, which has uniquely designed acrylic airfoils, allows a smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent natural convection from forming air currents inside the enclosure from causing an error in reading. Single-pan mechanical substitution balances maintain consistent response throughout the useful capacity, which is achieved by maintaining a constant load on the balance beam and thus the fulcrum by subtracting mass on the same side of the beam to which the sample is added. Electronic analytical scales measure the force needed to counter the mass being measured rather than using actual masses. As such they must have calibration adjustments made to compensate for gravitational differences. They use an electromagnet to generate a force to counter the sample being measured and output the result by measuring the force needed to achieve balance. Such a measurement device is called an electromagnetic force restoration sensor. Sources of error Some of the sources of error in weighing are:  Buoyancy – Objects in air develop a buoyancy force that is directly proportional to the volume of air displaced. The difference in density of air due to barometric pressure and temperature creates errors.  Error in the mass of reference weight  Air gusts, even small ones, which push the scale up or down  Friction in the moving components that causes the scale to reach equilibrium at a different configuration than a frictionless equilibrium should occur.  Settling airborne dust contributing to the weight  Mis-calibration over time, due to drift in the circuit's accuracy, or temperature change  Mis-aligned mechanical components due to thermal expansion or contraction of components  Magnetic fields acting on ferrous components  Forces from electrostatic fields, for example, from feet shuffled on carpets on a dry day  Chemical reactivity between air and the substance being weighed (or the balance itself, in the form of corrosion)  Condensation of atmospheric water on cold items  Evaporation of water from wet items  Convection of air from hot or cold items  Gravitational differences for a scale which measures force, but not for a balance.  Vibration and seismic disturbances  Microscope A microscope (from Ancient Greek (mikrós) 'small', and (skopéō) 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisible to the eye unless aided by a microscope. There are many types of microscopes, and they may be grouped in different ways. One way is to describe the method an instrument uses to interact with a sample and produce images, either by sending a beam of light or electrons through a sample in its optical path, by detecting photon emissions from a sample, or by scanning across and a short distance from the surface of a sample using a probe. The most common microscope (and the first to be invented) is the optical microscope, which uses lenses to refract visible light that passed through a thinly sectioned sample to produce an observable image. Other major types of microscopes are the fluorescence microscope, electron microscope (both the transmission electron microscope and the scanning electron microscope) and various types of scanning probe microscopes. History Although objects resembling lenses date back 4,000 years and there are Greek accounts of the optical properties of water-filled spheres (5th century BC) followed by many centuries of writings on optics, the earliest known use of simple microscopes (magnifying glasses) dates back to the widespread use of lenses in eyeglasses in the 13th century. The earliest known examples of compound microscopes, which combine an objective lens near the specimen with an eyepiece to view a real image, appeared in Europe around 1620. The inventor is unknown, even though many claims have been made over the years. Several revolve around the spectacle-making centers in the Netherlands, including claims it was invented in 1590 by Zacharias Janssen (claim made by his son) or Zacharias' father, Hans Martens, or both, claims it was invented by their neighbor and rival spectacle maker, Hans Lippershey (who applied for the first telescope patent in 1608), and claims it was invented by expatriate Cornelis Drebbel, who was noted to have a version in London in 1619. Galileo Galilei (also sometimes cited as compound microscope inventor) seems to have found after 1610 that he could close focus his telescope to view small objects and, after seeing a compound microscope built by Drebbel exhibited in Rome in 1624, built his own improved version. Giovanni Faber coined the name microscope for the compound microscope Galileo submitted to the Accademia dei Lincei in 1625 (Galileo had called it the occhiolino 'little eye'). Rise of modern light microscopes Carl Zeiss binocular compound microscope, 1914 The first detailed account of the microscopic anatomy of organic tissue based on the use of a microscope did not appear until 1644, in Giambattista Odierna's L'occhio della mosca, or The Fly's Eye. The microscope was still largely a novelty until the 1660s and 1670s when naturalists in Italy, the Netherlands and England began using them to study biology. Italian scientist Marcello Malpighi, called the father of histology by some historians of biology, began his analysis of biological structures with the lungs. The publication in 1665 of Robert Hooke's Micrographia had a huge impact, largely because of its impressive illustrations. A significant contribution came from Antonie van Leeuwenhoek who achieved up to 300 times magnification using a simple single lens microscope. He sandwiched a very small glass ball lens between the holes in two metal plates riveted together, and with an adjustable-by-screws needle attached to mount the specimen. Then, Van Leeuwenhoek re-discovered red blood cells (after Jan Swammerdam) and spermatozoa, and helped popularise the use of microscopes to view biological ultrastructure. On 9 October 1676, van Leeuwenhoek reported the discovery of micro-organisms. The performance of a light microscope depends on the quality and correct use of the condenser lens system to focus light on the specimen and the objective lens to capture the light from the specimen and form an image. Early instruments were limited until this principle was fully appreciated and developed from the late 19th to very early 20th century, and until electric lamps were available as light sources. In 1893 August Köhler developed a key principle of sample illumination, Köhler illumination, which is central to achieving the theoretical limits of resolution for the light microscope. This method of sample illumination produces even lighting and overcomes the limited contrast and resolution imposed by early techniques of sample illumination. Further developments in sample illumination came from the discovery of phase contrast by Frits Zernike in 1953, and differential interference contrast illumination by Georges Nomarski in 1955; both of which allow imaging of unstained, transparent samples. Introduction to Microscopes Botany was beginning to move beyond descriptive science into experimental science in the first half of the 18th century. Although the microscope was invented in 1590 it was only in the late 17th century that lens grinding by Antony van Leeuwenhoek provided the resolution needed to make major discoveries. Fig. (2): Robert Hooke's microscope which he described in 1665 Micrographia where he coined the biological use of the term cell Althought Robert Hooke (1635–1703) made the important general biological observations but the foundations of plant anatomy were laid by Italian Marcello Malpighi (1628–1694) of the University of Bologna and Royal Society Englishman Nehemiah Grew (1628–1711). These botanists explored what is now called developmental anatomy and morphology by carefully observing, describing and drawing the developmental transition from seed to mature plant, recording stem and wood formation. This work included the discovery and naming of parenchyma and stomata. Increased experimental precision combined with vastly improved scientific instrumentation was opening up exciting new fields. In 1936 Alexander Oparin (1894–1980) demonstrated a possible mechanism for the synthesis of organic matter from inorganic molecules. Mid-century transmission and scanning electron microscopy presented another level of resolution to the structure of matter, taking anatomy into the new world of “ultrastructure”, Fig. (3).  Fig. (3): Electron microscope constructed by Ernst Ruska in 1933. Types Microscopes can be separated into several different classes. One grouping is based on what interacts with the sample to generate the image, i.e., light or photons (optical microscopes), electrons (electron microscopes) or a probe (scanning probe microscopes). Alternatively, microscopes can be classified based on whether they analyze the sample via a scanning point (confocal optical microscopes, scanning electron microscopes and scanning probe microscopes) or analyze the sample all at once (wide field optical microscopes and transmission electron microscopes). Wide field optical microscopes and transmission electron microscopes both use the theory of lenses (optics for light microscopes and electromagnet lenses for electron microscopes) in order to magnify the image generated by the passage of a wave transmitted through the sample, or reflected by the sample. The waves used are electromagnetic (in optical microscopes) or electron beams (in electron microscopes). Resolution in these microscopes is limited by the wavelength of the radiation used to image the sample, where shorter wavelengths allow for a higher resolution. Scanning optical and electron microscopes, like the confocal microscope and scanning electron microscope, use lenses to focus a spot of light or electrons onto the sample then analyze the signals generated by the beam interacting with the sample. The point is then scanned over the sample to analyze a rectangular region. Magnification of the image is achieved by displaying the data from scanning a physically small sample area on a relatively large screen. These microscopes have the same resolution limit as wide field optical, probe, and electron microscopes. Scanning probe microscopes also analyze a single point in the sample and then scan the probe over a rectangular sample region to build up an image. As these microscopes do not use electromagnetic or electron radiation for imaging they are not subject to the same resolution limit as the optical and electron microscopes described above. Early microscopes, like Leeuwenhoek's, were called simple because they only had one lens. Simple scopes work like magnifying glasses. These early microscopes had limitations to the amount of magnification power. The Janssen added a second lens to magnify the image of the primary (or first) lens. Simple light microscopes of the past could magnify an object to 60X as in the case of Leuwenhoek's microscope, while Modern compound light microscopes, under optimal conditions, can magnify an object from 1000X to 2000X (times) the specimen’s original diameter. Image of Light Simple Microscope The microscope pictured is referred to as a compound light microscope. The term Compound means that the microscope is having more than one lens. The term light refers to the method by which light transmits the image to the user eye. Microscope is the combination of two words; "micro" meaning small and "scope" meaning view. The term light refers to the method by which light transmits the image to your eye. Compound deals with the microsc ope having more than one lens. Microscope is the combination of two words: Micro (meaning small) and scope (meaning view). The Fig. shows Onion base leaf as appeared by lower magnifigation (X 40).  Image of Light Compound Microscope. Compound Microscope Parts: 1. Eyepiece. 2. Nosepiece 3. Arm. 4. Objectives 5. Stage Clips 6.Objectives lenses 7.Knob 8.Slide 9.Stage 10.Coarse Adjustment Knob 11. Diaphragm 12. Light Source 13.Fine Adjustment knob 14. Power switch 15.Base  General view of Allium cepa leaf base as appeared by low magnification power (X40). Diagram Showing Light Traveling Through the light compound microscope. The term light refers to the method by which light transmits the image to your eye. The most recent developments in light microscope is the fluorescence microscopy. During the last decades of the 20th century, many techniques for fluorescent staining of cellular structures were developed samples. Anaphase stage “of mitosis” as appeared by fluorescent stain. Fluorescent Compound Light Microscope. The main groups of techniques involve targeted chemical staining of particular cell structures, for example, the chemical compound DAPI to label DNA, These techniques use these different fluorophores for analysis of cell structure at a molecular level in both live and fixed X-ray microscopes X-ray microscopes are instruments that use electromagnetic radiation usually in the soft X-ray band to image objects. Technological advances in X-ray lens optics in the early 1970s made the instrument a viable imaging choice. They are often used in tomography (see micro-computed tomography) to produce three dimensional images of objects, including biological materials that have not been chemically fixed. Currently research is being done to improve optics for hard X-rays which have greater penetrating power. Optical microscope The most common type of microscope (and the first invented) is the optical microscope. This is an optical instrument containing one or more lenses producing an enlarged image of a sample placed in the focal plane. Optical microscopes have refractive glass (occasionally plastic or quartz), to focus light on the eye or on to another light detector. Mirror-based optical microscopes operate in the same manner. Typical magnification of a light microscope, assuming visible range light, is up to 1,250× with a theoretical resolution limit of around 0.250 micrometres or 250 nanometres. This limits practical magnification to ~1,500×. Specialized techniques (e.g., scanning confocal microscopy, Vertico SMI) may exceed this magnification but the resolution is diffraction limited. The use of shorter wavelengths of light, such as ultraviolet, is one way to improve the spatial resolution of the optical microscope, as are devices such as the near-field scanning optical microscope. Sarfus is a recent optical technique that increases the sensitivity of a standard optical microscope to a point where it is possible to directly visualize nonmetric films (down to 0.3 nanometer) and isolated Nano-objects (down to 2 nm-diameter). The technique is based on the use of non-reflecting substrates for cross-polarized reflected light microscopy. Ultraviolet light enables the resolution of microscopic features as well as the imaging of samples that are transparent to the eye. Near infrared light can be used to visualize circuitry embedded in bonded silicon devices, since silicon is transparent in this region of wavelengths. In fluorescence microscopy many wavelengths of light ranging from the ultraviolet to the visible can be used to cause samples to fluoresce, which allows viewing by eye or with specifically sensitive cameras.  Unstained cells viewed by typical brightfield (left) compared to phase-contrast microscopy (right). Phase-contrast microscopy is an optical microscopic illumination technique in which small phase shifts in the light passing through a transparent specimen are converted into amplitude or contrast changes in the image. The use of phase contrast does not require staining to view the slide. This microscope technique made it possible to study the cell cycle in live cells. The traditional optical microscope has more recently evolved into the digital microscope. In addition to, or instead of, directly viewing the object through the eyepieces, a type of sensor similar to those used in a digital camera is used to obtain an image, which is then displayed on a computer monitor. These sensors may use CMOS or charge-coupled device (CCD) technology, depending on the application. Digital microscopy with very low light levels to avoid damage to vulnerable biological samples is available using sensitive photon-counting digital cameras. It has been demonstrated that a light source providing pairs of entangled photons may minimize the risk of damage to the most light-sensitive samples. In this application of ghost imaging to photon-sparse microscopy, the sample is illuminated with infrared photons, each of which is spatially correlated with an entangled partner in the visible band for efficient imaging by a photon-counting camera. Transmition Electron Microscope (TEM) In the early 20th century a significant alternative to the light microscope was developed, an instrument that uses a beam of electrons rather than light to generate an image. The German physicist, Ernst Ruska, working with electrical engineer Max Knoll, developed the first prototype electron microscope in 1931, a transmission electron microscope (TEM). The transmission electron microscope works on similar principles to an optical microscope but uses electrons in the place of light and electromagnets in the place of glass lenses. Use of electrons, instead of light, allows for much higher resolution.  Image of Transmission Electron Microscope (TEM). Transmition Electron Microscope (TEM) Microphotographs for plastid organelle and cell undergoing cytokinesis. Scanning Electron Microscope (SEM) Development of the transmission electron microscope was quickly followed in 1935 by the development of the scanning electron microscope by Max Knoll. Although TEMs were being used for research and became popular afterwards, Murphy, et. al., (2011) and Henry, (2003). Development of the transmission electron microscope was quickly followed in 1935 by the development of the scanning electron microscope by Max Knoll. Although TEMs were being used for research and became popular afterwards, Murphy, et. al., (2011) and Henry, (2003). Image of Scanning Electron Microscope (SEM). Scanning Electron Microscope (SEM) Microphotographs for Argemone mexicana seed and Plant Leaf surface.