A transmission electron microscope is a microscope which transmits a beam of electrons through an ultra thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera.
Transmission electron microscopes use extremely thin (0.5 µm or less) samples illuminated by the electron beam. Images are recorded by detecting the electrons that pass though the sample to a system of electromagnetic lenses which focus and enlarge the image on the fluorescent screen, photographic film or digital camera. Magnifications beyond 1,000,000x are attainable with a transmission electron microscope.