Scanning electron microscopy (SEM) has since it was commercially available in the sixties been used in the study of solid inorganic and organic materials at magnifications ranging from 10 to above 10000 times. Analysis tools are now including diffraction phenomena like EBSD for crystallographic studies The use of X-ray generated was early introduced and the performance of those EDS systems is enormous even if the basic principle of detection is almost the same. Even if the development of digital electronics is one important factor for todays performance of SEM, the most important factor for success is the generation of electron probe size with a small diameter to obtain as high resolving power as possible In addition to that the electron density plays a major role since the resolving power is dependent on peak to background ratio to get a sharp image, the development of bright guns is the most important factor.