Electron microscopes enable scientists to see extremely small particles.
In the 1920s, scientists discovered that electrons in a vacuum behave much like light except they can be manipulated with electric and magnetic fields. Since electrons curve around particles, these electron microscopes are vastly more powerful than traditional light-based microscopes.
Ruska invented the electron microscope at Siemens, as an employee. Eventually, he eventually left to serve as director of the Fritz Haber Institute then as a professor at the Technical University of Berlin. Although the microscope worked it did not produce especially useful images.
Eventually, Max Knoll invented the first Transmission Electron Microscope, refining Ruska’s invention. Knoll’s microscope produced vivid images. Later enhancements included the Scanning Tunneling Microscope.
Ruska won the Nobel Prize for physics in 1986.