Who started development of the first electron microscope in 1931 which was the transmission electron microscope ( TEM ) ?
At this time , interest in the electron microscope had increased , with other groups , such as Paul Anderson and Kenneth Fitzsimmons of Washington State University , and Albert Prebus and James Hillier at the University of Toronto who constructed the first TEMs in North America in 1935 and 1938 , respectively , continually advancing TEM design .