The first electron microscope was built by Ernst Ruska, who was born in 1906. He studied electrical engineering at the Technical College in Munich and later on in Berlin, where he began to work on vacuum technology. He also was very interested in the theoretical and experimental study of the optical behaviour of electron rays.
Hans Busch, who had been professor at the University of Jena since 1921, had invented the first magnetic lens. He had discovered that the magnetic field of a solenoid is able to focus an electron beam. Ruska occupied himself with this in the course of 1928 and 1929; during this period he recognized that the use of a pole cap shortens the focal length of such a lens.
In 1933 he used for the first time an electron microscope built by himself and Max Knoll which showed a better resolution than any light microscope. It was of the transmission type. For more than 40 years this column remained the prototype for new microscopes. Further developments mainly concerned the mechanical and electrical stability and the shielding against electromagnetic disturbances.
The first commercially available TEM was also developed by Ruska (1938, Siemens). The first Scanning Electron Microscope was developed in 1942. This was rather late, which is due to the electronics needed for scanning the electron probe across the specimen. It was commercially available not before 1965.
For his achievements in electron optics Ruska received 1986 the Nobel Prize for physics together with G. Binnig and H. Rohrer.
For further information about him please consult the following website.