1897
Discovery of the electron by J.J. Thompson
1924
P. De Broglie: particle/wave dualism
1927
Hans Busch: electron beams can be focused in an inhomogeneous
magnetic field.

Reproduced
with kind permission from the Ernst
Ruska Archiv e.V
1931
Ernst
Ruska and Max
Knoll built the first TEM
1938
First scanning transmission electron microscope (M. von Ardenne)
1939
First commercial TEM by Siemens (E. Ruska, B. von Borries)
~1940 Basic theoretical work on electron optics and electron lenses
(W. Glaser, O. Scherzer)
1943
Electron energy-loss spectroscopy EELS (J. Hillier)
1948 First TEM at ETH Zurich (report)
1951
X-ray spectroscopy (R. Castaing)
1956 First lattice image (J. Menter)
1957 Multi-slice method (J. Cowley, A. Moodie)
1964
First commercial SEM by Cambridge Instruments
~1970
First HRTEM microscopes with a resolution better than 4 Å
1986
Nobel prize for E. Ruska (together with G. Binning
and H. Rohrer, who developed the Scanning Tunneling Microscope)
~2000 Development of aberration-corrected TEM (H. Rose, M. Haider, K. Urban)
~2003
Aberration-corrected HRTEM microscopes reach sub-Ångstrøm
resolution (review)