Ernst Ruska (1906-1988), a German engineer and academic professor, built the first Electron Microscope in 1931, and the same principles behind his prototype still govern modern EMs.
electron microscope
While studying under Dr. Max Knoll at the technical university of Munich, he became interested in the possibility of electron microscopy as a solution to the limitations of optical or light microscopes.
Ruska understood that electron wavelengths are far shorter than light wavelengths and believed that, if he could find a way to apply this knowledge, he could develop a far more powerful microscope.
Together with Knolls, he developed the first electromagnetic lens, which focused a beam of electrons in lieu of an illuminator onto a source to create a magnified image.
Although this early version did not offer significant improvements to the optical microscope, Ruska was able to modify the electron lens and develop a more powerful version in the late 1930s.
He later worked as an electrical engineer for the Siemans Company, which manufactured the first electron microscope.
Ruska was awarded the Nobel Prize for Physics in 1986, credited with one of the most influential innovations of the 20th century.