An electron microscope is a type of microscope that uses a beam of electrons as a source of illumination to produce magnified images or electron diffraction patterns. Electron microscopes use electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing them to produce magnified images or electron diffraction patterns. The wavelength of an electron can be up to 100,000 times smaller than that of visible light, which gives electron microscopes a much higher resolution of about 0.1 nm, compared to about 200 nm for light microscopes. Electron microscopes can be used to investigate the ultrastructure of a wide range of biological and inorganic specimens, including microorganisms, cells, large molecules, biopsy samples, metals, and crystals. There are two main types of electron microscopes:
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Transmission electron microscope (TEM): In TEM, swift electrons go through a thin sample, and the resulting image is formed by the electrons that pass through the sample.
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Scanning electron microscope (SEM): In SEM, the image is formed by scanning a focused electron beam onto the surface of the specimen in a raster pattern. The interaction of the primary electron beam with the atoms near the surface causes the emission of particles at each point in the raster, which are then detected to form the image.
Electron microscopes are used in biomedical research to investigate the structure and composition of biological and non-biological specimens. They can resolve features that are more than 1 million times smaller than those visible with conventional optical microscopes. Electron microscopes are expensive to build and maintain, but the capital and running costs of confocal light microscope systems now overlap those of basic electron microscopes.
