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Micrograph
Micrograph
Micrograph
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100× light micrograph of Meissner's corpuscle at the tip of a dermal papillus
40× micrograph of a canine rectum cross section
A photomicrograph of a thin section of a limestone with ooids. The largest is approximately 1.2 mm in diameter. The red object in the lower left is a scale bar indicating relative size.
Approximately 10× micrograph of a doubled die on a coin, where the date was punched twice in the die used to strike the coin

A micrograph is an image, captured photographically or digitally, taken through a microscope or similar device to show a magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a microscope but is only slightly magnified, usually less than 10 times. Micrography is the practice or art of using microscopes to make photographs. A photographic micrograph is a photomicrograph, and one taken with an electron microscope is an electron micrograph.

A micrograph contains extensive details of microstructure. A wealth of information can be obtained from a simple micrograph like behavior of the material under different conditions, the phases found in the system, failure analysis, grain size estimation, elemental analysis and so on. Micrographs are widely used in all fields of microscopy.

Types

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Photomicrograph

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A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, a process referred to as photomicroscopy. At a basic level, photomicroscopy may be performed simply by connecting a camera to a microscope, thereby enabling the user to take photographs at reasonably high magnification.

Scientific use began in England in 1850 by Richard Hill Norris FRSE for his studies of blood cells.[1]

Roman Vishniac was a pioneer in the field of photomicroscopy, specializing in the photography of living creatures in full motion. He also made major developments in light-interruption photography and color photomicroscopy.

Photomicrographs may also be obtained using a USB microscope attached directly to a home computer or laptop.

Electron micrograph

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An electron micrograph is a micrograph prepared using an electron microscope.

Magnification and micron bars

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Micrographs usually have micron bars, or magnification ratios, or both.

Magnification is a ratio between the size of an object on a picture and its real size. Magnification can be a misleading parameter as it depends on the final size of a printed picture and therefore varies with picture size. A scale bar, or micron bar, is a line of known length displayed on a picture. The bar can be used for measurements on a picture. When the picture is resized the bar is also resized making it possible to recalculate the magnification. Ideally, all pictures destined for publication/presentation should be supplied with a scale bar; the magnification ratio is optional. All but one (limestone) of the micrographs presented on this page do not have a micron bar; supplied magnification ratios are likely incorrect, as they were not calculated for pictures at the present size.

Micrography as art

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The microscope has been mainly used for scientific discovery. It has also been linked to the arts since its invention in the 17th century. Early adopters of the microscope, such as Robert Hooke and Antonie van Leeuwenhoek, were excellent illustrators. Cornelius Varley's graphic microscope made sketching from a microscope easier with a camera-lucida-like mechanism. After the invention of photography in the 1820s the microscope was later combined with the camera to take pictures instead of relying on an artistic rendering.

Since the early 1970s individuals have been using the microscope as an artistic instrument. Websites and traveling art exhibits such as the Nikon Small World and Olympus Bioscapes have featured a range of images for the sole purpose of artistic enjoyment. Some collaborative groups, such as the Paper Project have also incorporated microscopic imagery into tactile art pieces as well as 3D immersive rooms and dance performances.

In 2015, photographer and gemologist Danny J. Sanchez photographed mineral and gemstone interiors in works referred to as "otherworldly".[2][3][4]

Photomicrography in smartphones

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A paper published in 2009 described a method of photomicrography in a smartphone using a free-hand technique.[5] An operator only need focus the camera through the eyepiece of a microscope and capture a photo normally. Later, adapters were designed for the purpose and sold commercially or home-made.[6] A home-made adapter was also made using scrap materials and a Coca-Cola aluminum can.[7]

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See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Micrograph

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from Grokipedia
A micrograph, also known as a , is a or captured through a that magnifies small objects or structures invisible to the , revealing intricate details at the cellular, molecular, or nanoscale level. These images are produced by projecting the magnified specimen onto a or , often using illumination techniques to enhance contrast and resolution. The practice of creating micrographs, or photomicrography, emerged in the early alongside the development of and . In the 1830s, William Henry Fox Talbot produced the first known photomicrographs of plant sections using solar microscopes and early photographic processes involving . By the 1860s, advancements such as aniline dyes for staining specimens and artificial lighting were pioneered by Lt. Col. Joseph J. Woodward at the Army Medical Museum, enabling detailed documentation of pathological tissues like cancer cells and significantly advancing medical diagnostics. Earlier microscopy observations, such as those in Robert Hooke's 1665 , relied on hand-drawn illustrations rather than photographs, marking the transition from qualitative sketches to precise photographic records. Micrographs are categorized by the type of used, each suited to specific scales and applications. micrographs, produced by optical microscopes, include brightfield images for basic absorption-based viewing of stained samples, phase contrast for enhancing transparent specimens without staining, and micrographs that highlight specific molecules using emitted from fluorophores. micrographs offer higher resolution (down to 0.2 nm) via (TEM) for internal structures or scanning electron microscopy (SEM) for surface topography, using electron beams instead of . These types enable visualization of entities from cells (∼10 μm) to viruses (∼100 nm). In scientific research and practice, micrographs are indispensable for fields like , , , and forensics. They facilitate disease diagnosis by imaging tumor cells or pathogens, such as in for detecting emerging viruses. In , SEM and TEM micrographs analyze nanostructures and defects in alloys or semiconductors. Forensics employs them to examine like fibers or biological fluids, while in , advanced techniques like confocal fluorescence microscopy support for and genetic studies. Overall, micrographs bridge the gap between human perception and the microscopic world, driving discoveries in diverse disciplines.

Fundamentals

Definition and Principles

A micrograph is a visual representation of an object or specimen at a , captured photographically or digitally through a or similar magnification device to reveal structural details invisible to the unaided eye. This relies on the interaction of illuminating agents—such as , electrons, or scanning probes—with the sample, which are then magnified and focused by optical or electronic systems to produce a discernible . Unlike a standard , which records macroscopic scenes using ambient or directed without inherent enlargement beyond normal vision, a micrograph necessitates specialized to visualize sub-millimeter features, often exceeding 100 times the original size. Photomicrography refers specifically to photography through a microscope for visualizing microscopic subjects at high magnifications, in contrast to photomacrography (or macrophotography), which involves close-up imaging of larger subjects at lower magnifications without a microscope. The fundamental principles of micrograph production center on magnification and resolution, governed by the physics of wave interactions and lens systems. Magnification enlarges the apparent size of the specimen by bending or deflecting the illuminating beam through lenses or fields, allowing observation of fine details; however, useful magnification is limited by resolution, the smallest distinguishable distance between points in the image. In optical microscopy, resolution is theoretically constrained by the Abbe diffraction limit, derived from the wave nature of light, expressed as d=λ2⋅NAd = \frac{\lambda}{2 \cdot \mathrm{NA}} where dd is the minimum resolvable distance, λ\lambda is the wavelength of light, and NA\mathrm{NA} is the numerical aperture of the objective lens, representing its light-gathering capacity. This limit arises because diffraction spreads light into overlapping patterns, blurring fine structures unless shorter wavelengths or higher NA values are employed; analogous principles apply in electron microscopy, where electron wavelengths (much shorter than visible light) enable sub-nanometer resolution. Micrograph acquisition typically involves sample preparation to enhance visibility and stability, such as sectioning thick specimens into thin slices for even illumination or applying stains that absorb or scatter the beam selectively to highlight cellular components. These steps are essential because unprepared samples often lack sufficient contrast against the background, rendering details indistinct. To address this, contrast enhancement techniques unique to exploit phase shifts or scattering; for instance, phase contrast converts differences in —transparent in brightfield—into amplitude variations for brighter or darker regions, while darkfield illumination scatters light only from the specimen, suppressing direct beam to isolate edges and particles. The earliest recorded microscopic depictions, sketched by in the late , laid the groundwork for these imaging principles.

Historical Development

The history of micrograph production began in the with the development of early microscopes, which enabled the first visual records of microscopic structures. , a Dutch tradesman and self-taught microscopist, crafted simple single-lens microscopes in the 1670s that magnified up to 270 times, allowing him to observe and sketch microorganisms such as and from samples like pond water and ; these hand-drawn illustrations, shared in letters to the Royal Society starting in 1674, served as proto-micrographs by providing the earliest detailed depictions of unseen worlds. Concurrently, English scientist advanced compound —using multiple lenses for greater magnification—and published in 1665, featuring engravings of cork cells, insect anatomy, and plant fibers observed at up to 50 times magnification, which popularized and influenced subsequent designs. The marked the transition to true photomicrographs—photographs taken through a —through the integration of with . In the 1830s, William Henry Fox Talbot produced the first known photomicrographs of plant sections using solar microscopes and early photographic processes involving . Building on this, English instrument maker John Benjamin Dancer advanced microphotography—tiny photographs mounted on slides for viewing under a —in , refining techniques to capture detailed subjects like portraits and text at scales as small as 1/16 inch, using early photographic methods to create permanent records beyond hand-drawing. processes, introduced in 1839, were adapted for in the 1840s to produce high-resolution positive images on silvered copper plates, while the wet-plate method—developed around 1851—became dominant by the 1850s–1870s for its sensitivity, enabling sharper photomicrographs of biological specimens and crystals through direct exposure of prepared plates. Twentieth-century innovations dramatically expanded micrograph capabilities with electron-based imaging. In 1931, German physicists and Max Knoll constructed the first prototype transmission electron microscope (TEM) using magnetic lenses to focus electron beams, achieving resolutions beyond optical limits; by 1933, Ruska produced the initial electron micrographs of specimens like aluminum films, magnifying up to 12,000 times and revealing sub-cellular details invisible to light microscopes. The (SEM), building on Knoll's 1935 designs for scanning electron beams, emerged in the 1940s–1960s for surface imaging, with Ruska's foundational earning him half of the 1986 (shared with scanning tunneling microscopy developers). The late introduced scanning probe techniques for atomic-scale resolution. In 1981, researchers and invented the (STM), which uses a sharp probe to measure quantum tunneling currents over conductive surfaces, producing the first atomic-resolution micrographs of crystals; this breakthrough, enabling manipulation and imaging at the scale, earned Binnig and Rohrer the other half of the 1986 alongside Ruska. The digital era transformed micrograph acquisition in the 1990s, shifting from film to electronic sensors. (CCD) cameras, initially developed in 1969 but adapted for microscopy in the 1980s, became standard by the mid-1990s, allowing real-time digital capture and processing of images with reduced noise and higher compared to photographic plates. A pivotal advancement came with (GFP), isolated by Osamu Shimomura in the 1960s and genetically engineered for live-cell labeling by and in the 1990s, enabling dynamic micrographs; their work on GFP's discovery and development was recognized with the 2008 . Key milestones in resolution trace this evolution: optical micrographs achieved ~1 μm detail in the 17th–19th centuries limited by light diffraction; TEM reached ~1 nm by the 1940s through electron wavelengths; and SPM techniques like STM attained atomic-scale (~0.1 nm) resolution from 1981 onward, surpassing prior limits by direct surface probing.

Types

Optical Micrographs

Optical micrographs, commonly referred to as photomicrographs, are photographs or digital s obtained through optical microscopes that utilize visible light to magnify and reveal fine details of specimens, typically ranging from cells to small organisms. These images are produced by various contrast-enhancing techniques tailored to improve visibility of transparent or low-contrast samples. transmits light directly through the specimen to create a basic , suitable for stained or opaque objects. scatters oblique illumination to render the specimen bright against a dark background, emphasizing edges and fine structures without staining. converts subtle phase shifts in refracted light into intensity differences, enabling unstained, live cell imaging with enhanced detail. Differential interference contrast (DIC) microscopy employs polarized light and prisms to generate a three-dimensional-like appearance by exploiting differences, ideal for observing surface relief in biological tissues. Polarized light microscopy uses crossed polarizers to reveal birefringence in anisotropic materials, such as crystals, minerals, and certain biological structures (e.g., collagen fibers or starch grains), producing characteristic interference colors and patterns that enable detailed identification and characterization. This technique is particularly valuable in gemology, as utilized by the Gemological Institute of America (GIA) for examining gemstones, and in materials science for studying crystal structures and stress patterns. Sample preparation for optical micrographs prioritizes transparency and contrast, often involving fixation to preserve structure, followed by sectioning or mounting. techniques, such as hematoxylin and eosin (H&E), are widely used for histological samples, where hematoxylin binds to nucleic acids in cell nuclei for blue-violet coloration, and stains cytoplasmic proteins and in pink to red hues, facilitating differentiation of tissue components. After staining, specimens are dehydrated, cleared, and mounted in media like or to match the of glass slides, minimizing light distortion and ensuring long-term stability for imaging. Optical micrographs offer key advantages, including real-time, non-destructive imaging of living samples at ambient conditions, which supports studies of dynamic cellular processes like mitosis without the need for vacuum environments. However, their resolution is fundamentally limited to about 200 nm laterally due to the diffraction of visible light wavelengths (approximately 400–700 nm), preventing visualization of sub-cellular structures smaller than this threshold. A seminal historical example of early microscopy observations is Robert Hooke's detailed engraving of a flea in his 1665 publication Micrographia, which showcased the microscope's potential to reveal intricate anatomical features previously invisible to the naked eye through detailed illustrations. Contemporary advancements in optical micrography include confocal scanning , which employs a focused beam scanned across the specimen in raster fashion, coupled with a pinhole to reject out-of-focus and produce thin optical sections for volumetric 3D reconstructions. extends this by selectively exciting fluorophores—molecules that absorb at specific excitation wavelengths (e.g., 488 nm for fluorescein) and re-emit at longer Stokes-shifted wavelengths—allowing targeted visualization of proteins or organelles via fluorescent tags in live or fixed samples.

Electron Micrographs

Electron micrographs are images produced by directing a beam of through or onto a specimen in a environment, where the interact with the sample to form contrast based on or transmission. This technique achieves resolutions down to approximately 0.1 nm, far surpassing optical , owing to the short de Broglie of accelerated , given by λ=h/p\lambda = h / p, where hh is Planck's constant and pp is the 's . In (TEM), a high-energy beam passes through ultra-thin specimens typically thinner than 100 nm, producing a two-dimensional projection of internal structures. Biological samples are prepared by chemical fixation with agents like , embedding in epoxy resin for support, sectioning to achieve the required thinness, and with such as uranyl acetate or to enhance contrast by selectively scattering electrons. This method excels in visualizing ultrastructures, including viral particles and organelles, enabling detailed studies of their morphology and internal organization. Scanning microscopy (SEM) focuses on surface by raster-scanning a focused beam over the specimen, detecting signals from electron-sample interactions to reveal . , emitted from near the surface, provide high-resolution details of surface features and contribute to a three-dimensional-like appearance due to the instrument's large , while backscattered electrons offer compositional contrast. For non-conductive biological samples, a thin layer of is sputtered onto the surface to improve electrical conductivity, preventing charging artifacts under the electron beam. Electron microscopy techniques are constrained by the need for high to maintain beam integrity and prevent by air molecules, necessitating dehydrated and fixed specimens that cannot be observed in a native, living state. Additionally, the high-energy beam induces in biological samples through , bond breakage, and mass loss, limiting usable doses to around 20–50 electrons per square ångstrom (equivalent to 2,000–5,000 per square nanometer) before significant structural disruption occurs.

Scanning Probe Micrographs

Scanning probe micrographs are images produced by raster-scanning a physical probe across a sample surface to map its topography and properties at the nanoscale, with key techniques including (AFM) and scanning tunneling microscopy (STM). These methods rely on direct physical or electrical interactions between the probe and sample, enabling high-resolution imaging without the use of light or electron beams. Atomic force microscopy generates micrographs by detecting minute forces between a sharp tip attached to a flexible and the sample surface, such as van der Waals or electrostatic interactions. The cantilever's deflection, measured via reflection or other sensors, provides feedback to maintain a constant force or amplitude, allowing reconstruction of surface features. AFM operates in multiple modes to suit different samples: contact mode, where the tip drags across the surface in constant touch; tapping mode, which oscillates the cantilever to intermittently contact the sample, reducing wear on soft materials; and non-contact mode, which senses long-range attractive forces without physical contact. These modes enable resolutions as fine as 0.1 nm laterally and sub-angstrom vertically, capturing not only but also mechanical properties like and . Scanning tunneling microscopy produces micrographs by measuring the quantum tunneling current that flows between a conductive probe tip and a conductive sample when separated by a few angstroms. Invented in by and at Zurich, who were awarded the 1986 for this breakthrough, STM adjusts the tip height via piezoelectric actuators to keep the current constant, yielding atomic-scale images of surface electronic structure. It excels in visualizing atomic arrangements on metal and semiconductor surfaces, with applications in materials science for studying adsorption and reconstruction. Scanning probe techniques offer distinct advantages, including operation in ambient air, liquids, or without requiring sample conductivity for AFM, facilitating 3D profiling of diverse materials from insulators to biomolecules. Unlike vacuum-dependent methods, they support real-time imaging under physiological conditions. However, limitations include relatively slow scanning speeds due to mechanical feedback loops, typically on the order of minutes per image, and potential tip contamination or sample damage in aggressive modes.

Technical Aspects

Magnification and Resolution

Magnification in microscopy refers to the ratio of the image size to the actual size of the specimen, typically expressed as M=hihoM = \frac{h_i}{h_o}, where hih_i is the height of the image and hoh_o is the height of the object. This enlargement allows visualization of fine details otherwise invisible to the , but it must be distinguished from resolution, as excessive magnification without sufficient detail clarity results in "empty magnification." Useful magnification is limited by the system's resolving power, ensuring that the enlarged image retains discernible features; beyond this, the image appears blurry and lacks additional information. Resolution defines the smallest distance between two points in the specimen that can be distinguished as separate in the micrograph, fundamentally constrained by the of the illumination source and the used. In optical microscopy, the Abbe limit provides the theoretical resolution d=0.61λNAd = \frac{0.61 \lambda}{NA}, where λ\lambda is the of and NANA is the of the objective lens, typically yielding a practical limit around 0.2 μm for visible . For electron microscopy, resolution improves dramatically due to the shorter de Broglie of , given by λe=h2meV\lambda_e = \frac{h}{\sqrt{2 m e V}}
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