The Transmission Electron Microscope (TEM) has been used in all areas of biological and biomedical investigations besides other fields because of its ability to view the finest cell structures. It is also used as a diagnostic tool in hospital pathology labs. For the crystallographer, metallurgist or semiconductor research scientist, current high voltage/high resolution TEMs, utilizing 200 keV to 1 MeV, have permitted the routine imaging of atoms, allowing materials researchers to monitor and design materials with custom-tailored properties. With the addition of energy dispersive X-ray analysis (EDXA) or energy loss spectrometry (EELS), the TEM can also be used as an elemental analysis tool, capable of identifying the elements in areas less than 0.5µm in diameter. The transmission electron microscope (TEM) operates on the same basic principles as the light microscope but uses electrons instead of light. What can be seen with a light microscope is limited by the wavelength of light, but TEMs uses electrons as "light source" and their much lower wavelength makes it possible to get a resolution a thousand times better than with a light microscope. Objects to the order of a few angstrom and small details in the cell or different materials down to near atomic levels can be studied. The possibility for high magnifications has made the TEM a valuable tool in both medical, biological and materials research.