Electron microscope is a large sized instrument which has an internal vacuum, high voltage (50,000 to 1,00,000 volts), a cooling system, a fast beam of electrons (0.54˚A wavelength), a cathode filament of tungsten, electromagnetic lenses (each having a coil of wire enclosed in soft iron casing) for focussing, magnification and projection and a fluorescent screen or photographic plate for observation. Wavelength of electron beam is 10,000 times shorter than wavelength of visible light. As a result, resolving power of electron microscope is very high. Resolving power of unaided human eye is 100 micrometer and 2 to 10˚A for electron microscope.