Microscopes and microscopy

MICROSCOPES AND MICROSCOPY

Chapter 7

The Basics of the Microscope

• A microscope is an optical instrument that uses a lens or a combination of lenses to magnify and resolve the fine details of an object.

• The earliest methods for examining physical evidence in crime laboratories relied almost solely on the microscope to study the structure and composition of matter.


• The microscope is still one of the most used tools in a crime laboratory for analyzing evidence, even with the advent of other modern instrumentation.


• The earliest and simplest microscope was the single lens commonly referred to as a magnifying glass. The handheld magnifying glass makes things appear larger than they are because of the way light rays are refracted, or bent, in passing from the air into the glass, and back to the air.

• The magnified image is observed by looking through the lens.

• Since the image appears to be on the same side of the lens as the object, it cannot be projected onto a screen. Such images are termed virtual images and they appear upright, not inverted. Figure 1 presents an illustration of how a simple magnifying lens operates. The object (in this case the subject is a rose) is being viewed with a simple bi-convex lens. Light reflected from the rose enters the lens in straight lines as illustrated in Figure 1. This light is refracted and focused by the lens to produce a virtual image on the retina. The image of the rose is magnified because we perceive the actual size of the object (the rose) to be at infinity because our eyes trace the light rays back in straight lines to the virtual image (Figure 1). This is discussed in greater detail below.

Simple Lenses

• The ordinary magnifying glass can achieve a magnification of about 5 to 10 times. Higher magnifying power is obtainable only with a compound microscope, constructed of two lenses mounted at each end of a hollow tube. The object to be magnified is placed under the lower lens, called the objective lens, and the magnified image is viewed through the upper lens, called the eyepiece lens.

History and Anatomy of the Microscope

• As shown in the figure to the left, the objective lens forms a real, inverted, magnified image of the object. They eyepiece, acting just like a magnifying glass, further magnifies this image into a virtual image, which is seen by the eye. The combined magnifying power of both lenses can produce an image magnified up to 1,500 times.


• Microscopes are instruments designed to produce magnified visual or photographic images of small objects. The microscope must accomplish three tasks: produce a magnified image of the specimen, separate the details in the image, and render the details visible to the human eye or camera. This group of instruments includes not only multiple-lens designs with objectives and condensers, but also very simple single lens devices that are often hand-held, such as a magnifying glass.


• The microscope illustrated in Figure 1 is a simple compound microscope invented by British microscopist Robert Hooke sometime in the 1660s. This beautifully crafted microscope has an objective lens near the specimen and is focused by turning the body of the microscope to move the objective closer to or farther from the specimen. An eyepiece lens is inserted at the top of the microscope and, in many cases, there is an internal "field lens" within the barrel to increase the size of the viewfield. The microscope in Figure 1 is illuminated through the oil lamp and water-filled spherical reservoir, also illustrated in Figure 1. Light from the lamp is diffused when it passes through the reservoir and is then focused onto the specimen with a lens attached to the reservoir. This early microscope suffered from chromatic (and spherical) aberration, and all images viewed in white light contained "halos" that were either blue or red in color.


• Since so many microscope users rely upon direct observation, it is important to understand the relationship between the microscope and the eye. Our eyes are capable of distinguishing color in the visible portion of the spectrum: from violet to blue to green to yellow to orange to red; the eye cannot perceive ultraviolet or infrared rays. The eye also is able to sense differences in brightness or intensity ranging from black to white and all the gray shades in between. Thus, for an image to be seen by the eye, the image must be presented to the eye in colors of the visible spectrum and/or varying degrees of light intensity.


• The eye receptors of the retina used for sensing color are the cone cells; the cells for distinguishing levels of intensity, not in color, are the rod cells. These cells are located on the retina at the back of the inside of the eye. The front of the eye (see Figure 2), including the iris, the curved cornea, and the lens are respectively the mechanisms for admitting light and focusing it on the retina.


• More than five hundred years ago, simple glass magnifiers were developed. These were convex lenses (thicker in the center than the periphery). The specimen or object could then be focused by use of the magnifier placed between the object and the eye. These "simple microscopes" could spread the image on the retina by magnification through increasing the visual angle on the retina.



• The "simple microscope" or magnifying glass reached its highest state of perfection, in the 1600's, in the work of Anton von Leeuwenhoek who was able to see single-celled animals (which he called "animalcules") and even some larger bacteria with a simple microscope similar to the one illustrated in Figure 3. The image produced by such a magnifier, held close to the observer's eye, appears as if it were on the same side of the lens as the object itself. Such an image, seen as if it were ten inches from the eye, is known as a virtual image and cannot be captured on film.

Anton Von Leeuwenhoek (1632-1723)Father of Microbiology

• Around the beginning of the 1600's, through work attributed to the Janssen brothers (see the microscope in Figure 4) in the Netherlands and Galileo in Italy, the compound microscope was developed. In its simplest form, it consisted of two convex lenses aligned in series: an object glass (objective) closer to the object or specimen; and an eyepiece (ocular) closer to the observer's eye (with means of adjusting the position of the specimen and the microscope lenses). The compound microscope achieves a two-stage magnification. The objective projects a magnified image into the body tube of the microscope and the eyepiece further magnifies the image projected by the objective.


Zacharias JanssenMicroscope

Galileo’s Microscope by Zacharias Janssen

(circa 1590)

• The eighteenth and nineteenth centuries witnessed a great improvement in the mechanical and optical quality of compound microscopes. Advances in machine tools allowed more sophisticated parts to be fabricated and, by the mid 1800's, brass was the alloy of choice for the production of high-quality microscopes. A number of British and German microscope manufacturers flourished during this time period. Their microscopes varied widely in design and production quality, but the overall principles defining their optical properties remained relatively constant. The microscope illustrated in Figure 5 was manufactured by Hugh Powell and Peter Lealand about 1850. The tripod base provided a sturdy support for the microscope, which many people consider the most advanced of its period.


• During the first quarter of the twentieth century, many microscope manufacturers had begun substituting cast iron for brass in microscope frames and stages. Iron was much cheaper and could be not be distinguished from brass when painted black. They also started to electroplate many of the critical brass components such as knobs, objective barrels, nosepieces, eyepieces, and mechanical stage assemblies (illustrated in Figure 6). These early twentieth century microscopes still subscribed to a common design motif. They were monocular with a substage mirror that was used with an external lamp to illuminate the specimen. A typical microscope of the period is the Zeiss Laboratory microscope pictured in Figure 6. This type of microscope is very functional and many are still in use today.


• Modern microscopes far exceed the design specifications of those made prior to the mid 1900's. Glass formulations are vastly improved allowing greater correction for optical aberration than ever before, and synthetic anti-glare lens coatings are now very advanced. Integrated circuit technology has allowed manufacturers to produce "smart" microscopes that incorporate microprocessors into the microscope stand. Photomicrography in the late twentieth century is easier than ever before with auxiliary attachments that monitor light intensity, calculate exposure based on film speed, and automatically perform complicated tasks such as bracketing, multiple exposure, and time-lapse photography.


• The microscope illustrated in Figure 7 is an Olympus Provis AX70 research microscope. This microscope represents the latest state-of-the-art design that incorporates multiple illuminators (episcopic and diascopic), analyzers and polarizers, DIC prisms, fluorescence attachments, and phase contrast capabilities. The photomicrography system is the ultimate in sophistication and performance featuring spot measurement, automatic exposure control, and zoom magnification for flexible, easy framing. The Y-shaped frame is designed to be user-friendly by offering the maximum in operator comfort and ease of use.


• The optical principles of the compound microscope are incorporated into the basic design of different types of light microscopes. The microscopes most applicable for examining forensic specimens are as follows:– The compound microscope– The comparison microscope– The stereoscopic microscope– The polarizing microscope– The microspectrophotometer


• The parts of the compound microscope are illustrated at the left. This microscope consists of a mechanical system, which supports the microscope, and an optical system.

• The mechanical system of the compound microscope is composed of six main parts:– BASE: the support on which the instrument rests

– ARM: a C-shaped upright structure, hinged to the base, that supports the microscope and acts as a handle for carrying

– STAGE: The horizontal plate on which the specimens are placed for study. The specimens are normally mounted on glass slides that are held firmly in place on the stage by stage clips.

– BODY TUBE: A cylindrical hollow tube on which the objective and eyepiece lenses are mounted at opposite ends. This tube is merely a corridor through which light passes from one lens to another.

– COARSE ADJUSTMENT: This knob focuses the microscope lenses on the specimen by raising and lowering the stage.

– FINE ADJUSTMENT: The movements effected by this knob are similar to those of the coarse adjustment but are of a much smaller magnitude.

The Compound Microscope

• The optical system is made up of four parts:– ILLUMINATOR: Most modern

microscopes use artificial light supplied by a lightbulb to illuminate the specimen being examined. If the specimen is transparent, the light is directed up toward and through the specimen stage from an illuminator built into the base of the microscope. This is known as transmitted illumination. When the object is opaque – that is, not transparent – the light source must be placed above the specimen so that it can reflect off the specimen’s surface and into the lens system of the microscope. This type of illumination is known as vertical or reflected illumination.


– CONDENSER: The condenser is a lens system under the microscope stage that collects light rays from the base illuminator and focuses them on the specimen. The simplest condenser is known as the Abbé condenser. It consists of two lenses held together in a metal mount. The condenser also includes an iris diaphragm that can be opened or closed to control the amount of light passing into the condenser.

– OBJECTIVE LENS: This is the lens positioned closest to the specimen. To facilitate changing from one objective lens to another, several objectives are mounted on a revolving nosepiece or turret located about the specimen. Most microscopes are parfocal, meaning that when the microscope is focused with one objective in position, the other objective can be rotated into place by revolving the nosepiece while the specimen remains very nearly in correct focus.

– EYEPIECE or OCULAR LENS: This is the lens closest to the eye. A microscope with only one eyepiece is monocular; one constructed with two eyepieces is binocular.


Each microscope lens is inscribed with a number signifying its magnifying power. The image viewed by the microscopist will have a total magnification equal to the product of the magnifying power of the objective and eyepiece lenses. For example, an eyepiece lens with a magnification of 10 times (10x) used in combination with an objective lens of 10x has a total magnification power of 100x. Most forensic work requires a 10x eyepiece in combination with either a 4x, 10x, 20x, or 45x objective. The respective magnifications will be 400x, 100x, 200x, and 450x.

The Compound MicroscopeMagnification and Resolution

• In addition, each objective lens is inscribed with its numerical aperture. (N.A.). The ability of an objective lens to resolve details into separate images instead of one blurred image is directly proportional to the numerical aperture value of the objective lens. For example, an objective lens of N.A. 1.30 can separate details at half the distance of a lens with an N.A. of 0.65. The maximum useful magnification of a compound microscope is approximately 1,000 times the N.A. of the objective being used. This magnification is sufficient to permit the eye to see all the detail that can be resolved. Any effort to increase the total magnification beyond this figure will yield no additional detail and is referred to as empty magnification.


• The experienced microscopist weighs a number of important factors before choosing a magnifying power:– FIELD OF VIEW: A first consideration must be the size of the specimen

area, or the field of view, that the examiner wishes to study. As magnifying power increases, the field of view decreases. Thus, it is best to first select a low magnification in which a good general overall view of the specimen is seen, and to switch later to a higher power in which a smaller portion of the specimen can be viewed in more detail.

– DEPTH OF FOCUS: The depth of focus is also a function of magnifying power. After a focus has been achieved on a specimen, the depth of focus defines the thickness of that specimen. Areas above and below this region will be blurred and can be viewed only when the focus is readjusted. Depth of focus decreases as magnifying power increases.


• Forensic microscopy often requires a side-by-side comparison of specimens. This kind of examination can be best performed with a comparison microscope, such as the one pictured at left.

• Basically, the comparison microscope is two compound microscopes combined into one unit. The unique feature of its design is that it uses a bridge incorporating a series of mirrors and lenses to join two independent objective lenses into a singular binocular unit.

The Comparison Microscope

• A viewer looking through the eyepiece lenses of the comparison microscope observes a circular field, equally divided into two parts by a fine line. The specimen mounted under the left-hand objective appears in the left half of the field, and the specimen mounted under the right-hand objective appears in the left half of the field.

• Comparison microscopes designed to compare opaque objects, such as bullets and cartridge casings, are equipped with vertical or reflected illumination.

• Comparison microscopes used to compare hairs or fibers use transmitted illumination.

The Comparison Microscope

The Stereoscopic Microscope• The details that characterize the structures of

many types of physical evidence do not always require examination under very high magnifications. For such specimens, the stereoscopic microscope has proven quite adequate, providing magnifying powers from 10x to 125x. This microscope has the advantage of presenting a distinctive three-dimensional image of an object. Also, whereas the image formed by the compound microscope is inverted and reversed, the stereoscopic microscope is more convenient because prisms in its light path create a right-side-up image.

• The stereoscopic microscope shown is actually two monocular compound microscopes properly spaced and aligned to present a three dimensional image of a specimen to the viewer, who looks through both eyepiece lenses.

• The stereoscopic microscope is undoubtedly the most frequently used and versatile microscope found in the crime laboratory. Its wide field of view and great depth of focus make it an ideal instrument for locating trace evidence in debris, garments, and tools. Furthermore, its potentially large working distance (the distance between the objective lens and the specimen) makes it ideal for microscopic examination of big, bulky items. When fitted with vertical illumination, the stereoscopic microscope becomes the primary tool for characterizing physical evidence as diverse as paint, soil, gunpowder residues, and marijuana.

The Stereoscopic Microscope

• Before we can discuss the polarizing light microscope, we must first talk about the theory of light. As with all matter, knowledge of the nature and behavior of light is fundamental to understanding physical properties important to the examination of forensic evidence. Two simple models explain light’s behavior. The first model describes light as a continuous wave; the second depicts it as a stream of discrete energy particles. Together, these two very different descriptions explain all of the observed properties of light, but by itself, no one model can explain all the facets of behavior of light.

The Polarizing MicroscopeThe Theory of Light

• The wave concept depicts light as having an up-and-down motion of a continuous wave, as shown below. Such a wave can be characterized by two distinct properties: wavelength and frequency.

Light as a Wave

Wavelength and Wave Motion• The distance between two consecutive crests (high points) or

troughs (low points) of a wave is called the wavelength; it is designated by the Greek letter lambda (λ) and is typically measured in nanometers (nm), or millionths of a meter. The number of crests (or troughs) passing any one given point in time is defined as the frequency of the wave. Frequency is normally designated by the letter ƒ and is expressed in cycles per second (cps). Frequency and wavelength are inversely proportional to one another, as shown in the relationship

F = c/λwhere c equals the speed of light.

Wavelength and Wave MotionWave length Peak

Amplitude

Trough

• Many of us have held a glass prism up toward that sunlight and watched it transform light into the colors of the rainbow. The process of separating light into its component colors is called dispersion. Visible light usually travels at a constant velocity of nearly 300 million meters per second. However, on passing through a prism, each color component of light is slowed to a speed slightly different from those of the others, causing each component to bend at a different angle as it emerges from the prism. The bending of light waves because of the change in velocity if called refraction.

Wavelength and Wave Motion

Wavelength and Wave MotionThe observation that a substance has a color is consistent with this description of white light. For example, when light passes through a red glass, the glass absorbs all the component colors of light except red, which passes through or is transmitted by the glass. Like wise, one can determine the color of an opaque object by observing its ability to absorb some of the component colors of light while reflecting others back to the eye. Color is thus a visual indication that objects absorb certain portions of visible light and transmit or reflect others. Scientists have long recognized this phenomenon and have learned to characterize different chemical substances by the type and quantity of light they absorb. This has important applications for the identification and classification of forensic evidence.

The Multispectral SunThis animation shows views of the Sun at various frequencies across the electromagnetic spectrum. Note how different features and regions of the Sun are visible in the different views. The visible light view shows the photosphere, including several sunspots. The infrared view shows the lower chromosphere immediately above the photosphere, where temperatures are still relatively cool. Most of the high energy photons that produce the UV and X-ray views come from higher up in the Sun's hot atmosphere. Notice how the areas of the atmosphere above sunspots tend to be especially bright in the X-ray and UV views. Sunspots are visible indicators of magnetic disturbances on the Sun that high energy phenomena such as solar flares and coronal mass ejections. Most of the individual views portray the Sun as seen through a very narrow range of wavelengths; for example, the IR view is just a narrow band of infrared "light" with a wavelength around 1,083 nanometers (as opposed to the entire IR portion of the spectrum, which ranges across wavelengths from 750 nm to 1 mm), while the first UV image is centered around a wavelength of 30.4 nanometers. These narrow wavelength "windows" in the EM spectrum are actually the "fingerprints" of specific elements at specific temperatures.

• The observation that a substance or object has color is consistent with the description of white light. For example, when light passes through red glass, the glass absorbs all the component colors of light except red, which passes through or is transmitted by the glass. Likewise, one can determine the color of an opaque object by observing its ability to absorb some of the component colors of light while reflecting others back to the eye.

Wavelength and Wave Motion

• Color is thus a visual indication that objects absorb certain portions of visible light and transmit or reflect others. Scientists have long recognized this phenomenon and have learned to characterize different chemical substances by the type and quantity of light they absorb. This has important applications for the identification and classification of forensic evidence.

Perception of COLOR

The Electromagnetic Spectrum

• Similarly, the range of colors that make up the visible spectrum can be correlated with frequency. For instance, the lowest frequencies of visible light are red; waves with a lower frequency fall into the invisible infrared (IR) region. The highest frequencies of visible light are violet, waves with a higher frequency extend into the invisible, ultraviolet (UV) region. No definite boundaries exist between any colors or regions of the electromagnetic spectrum; instead, each region is composed of a continuous range of frequencies, each blending into the other.

• Ordinarily, light in any region of the ES is a collection of waves possessing a range of wavelengths. Under normal circumstances, this light comprises waves that are all out of step with each other (incoherent light). However, scientists can produce light that has all its waves pulsating in unison. This is called a laser (light amplification by stimulated emission of radiation). Light in this form is very intense and can be focused on a very small area. Laser beams can be focused to pinpoints that are so intense that they can zap microscopic holes in a diamond.

Lasers

• The light’s wavelike motion in space can be invoked to explain many facets of its behavior. The waves that compose a beam of light can be pictured as vibrating in all directions perpendicular to the direction in which the light is traveling. However, when a beam of light passes through certain types of specially fabricated crystalline substances, it emerges vibrating in only one plane. Light that is confined to a single plane of vibration is said to be plane-polarized.

The Polarizing Microscope

• The device that creates polarized light is called a polarizer.

• Because polarized light appears no different to the eye from ordinary light, special means must be devised for detecting it. This is accomplished simply placing a second polarizing crystal, called an analyzer, in the path of the polarized beam. If the polarizer and analyzer are aligned parallel to each other, the polarized light passes through and is seen by the eye. If, on the other hand, the polarizer and analyzer are set perpendicular to one another, or are “crossed”, no light penetrates, and the result is total darkness or extinction.


• Essentially, the polarizer is placed between the light source and the sample stage to polarize the light before it passes through the specimen. The polarized light penetrating the specimen must then pass through an analyzer before it reaches the eyepiece and finally the eye. Normally the polarizer and analyzer are “crossed” so that when no specimen is in place, the field appears dark. However, introducing a specimen that polarizes light reorients the polarized light, allowing it to pass through the analyzer. This result produces vivid colors and intensity contrasts that make the specimen readily distinguishable.


• Few instruments in a crime laboratory can match the versatility of the microscope. The microscope’s magnifying power is indispensable for finding minute traces of physical evidence. Many items of physical evidence can be characterized by a microscopic examination of their morphological features. Likewise, the microscope can be used to study how light interacts with the material under investigation, or it can be used to observe the effects that other chemical substances have on such evidence. Each of these features allows an examiner to better characterize and identify physical evidence. Recently, linking the microscope to a computerized spectrophotometer has added a new dimension to its capability. This combination has given rise to a new instrument called the microspectrophotometer.

The Microspectrophotometer

The MicrospectrophotometerWith the development of the microspectrophotometer, a forensic analyst can view a particle under a microscope while a beam of light is directed at the particle to obtain its absorption spectrum. An absorption spectrum is the characteristic pattern of dark lines or bands that occurs when electromagnetic radiation is passed through an absorbing medium into a spectroscope. An equivalent pattern occurs as colored lines or bands in the emission spectrum of that medium. The range of frequencies of electromagnetic radiation readily absorbed by a substance by virtue of its chemical composition is unique to that substance and creates a “fingerprint”.

• Depending on the type of light employed, an examiner can acquire either a visible or an IR spectral pattern of the substance being viewed under the microscope. The obvious advantage of this approach is to provide added information to characterize trace quantities of evidence. A microspectrophotometer designed to measure the uptake of visible light by materials is shown on the previous slide.


Absorption spectrum of the planet Gliese 581g to analyze the possibility of the presence of life, or the capability of the planet to support life (similar to ours).

• Visual comparison of color is usually one of the first steps in examining paint, fiber and ink evidence. Such comparisons are easily obtained using a comparison microscope. A forensic scientist can use the microspectrophotometer to compare the color of materials visually while plotting an absorption spectrum for each item under examination. This displays the Exact wavelengths at which each item absorbs light in the visible-light spectrum.

Another emerging technique in forensicscience is the use of the infrared spectro-photometer to examine fibers and paints.The “fingerprint” IR spectrum is unique for each chemical substance.


• All the microscopes described thus far use light coming off the specimen to produce a magnified image. The scanning electron microscope (SEM) is, however, a special case in the family of microscopes . The image is formed by aiming a beam of electrons onto the specimen and studying electron emissions on a closed TV circuit.

The Scanning Electron Microscope(SEM)

• Palynology: The branch of science concerned with the study of pollen, spores , and similar palynomorphs, living and fossil.

• Forensic Palynology: the use of pollen and spore evidence in legal cases (Mildenhall, 1982). In its broader application, the field of forensic palynology also includes legal information derived from the analysis of a broad range of microscopic organisms--such as dinoflagellates, acritarchs, and chitinozoans--that can be found in both fresh and marine environments (Faegri et al., 1989). However, in most sampling situations forensic palynologists rarely encounter these other types of organisms because most are restricted to fossil deposits. Studies of palynomorphs trapped in materials associated with criminal or civil investigations are slowly gaining recognition as valuable forensic techniques.

Introduction to Forensic Palynology

• Of the many plant species on earth, more than half a million produce pollen or spores. The pollen or spores produced by each species has a unique type of ornamentation and morphology. This means that pollen or spores can be identified and used to provide links between a crime scene and a person or object if examined by a trained analyst. This technique is called forensic palynology and includes the collection and examination of pollen and spores connected with crime scenes, illegal activities, or terrorism. Microscopy is the principal tool used in the field of forensic palynology.

Forensic Palynology: Pollen and Spores as Evidence

• In nature, pollen grains are the single-celled male gametophytes of seed-bearing plants. The pollen grain wall (exine) is durable because it protects and carries the sperm cells needed for plant reproduction. Spores consist of both male and female gametes of plants such as algae, fungi, mosses, and ferns. Pollen-producing plants are either anemophilous (their pollen is dispersed by wind) or entomophilous (their pollen is carried and dispersed by insects or small animals).

Forensic Palynology: Characteristics of Spores and Pollen

• Fairly precise geographical locations can often be identified by the presence of different mixtures of airborne pollens produced by anemophilous plants. For example, it may be possible to identify a geographical origin by a profile of the pollen samples retrieved from a suspect’s clothing simply by the type and percentages of airborne pollen grains.


• Entomophilous plants usually produce a small amount of pollen that is very sticky in nature. Therefore, this type of pollen is very rarely deposited on clothing or other objects except by direct contact with the plant. This information is useful when reconstructing the events of a crime because it indicates that the clothing, a vehicle, or other objects may have come into direct contact with plant types found at a crime scene.


• Both spores and pollen are microscopic in size and are produced by the adult plants and dispersed by the millions, and both can be analyzed using similar methods that use a variety of microscopic techniques. Using a compound light microscope with magnification capabilities up to 1,000x, analysts usually can identify pollen and spores as coming from a specific plant family or genus, and at times even a unique species. However, often the pollen or spores of related species may appear so similar that identification of the species is possible only with careful analysis using an SEM.

Forensic Palynology: Analysis of Spores and Pollen

• Unique shapes, aperture type, and surface ornamentation are typically used to identify spore samples. Useful features for characterizing pollen grains include shape, apertures, and wall and surface sculpturing. Shapes of pollen grains include spheres, triangles, ellipses, hexagons, pentagons, and many other geometric variations. Apertures are the openings on pollen grains from which the pollen tube grows and carries the sperm to the egg to complete fertilization.


• To avoid destruction or contamination, early collection of forensic pollen samples for analysis is important and should be completed as soon as possible at a crime scene by a trained palynologist. This kind of expert’s first task is to calculate the estimated production and dispersal patterns of spores and pollen (called the pollen rain) for the crime scene or area of interest, and then using that information to produce a kind of “pollen fingerprint” of that location.


Microscopes and microscopy

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