(1906–88), German physicist. Born in Heidelberg, Germany, Ruska was a corecipient of the 1986 Nobel prize in physics for his invention of the electron microscope. He was a researcher at Siemens-Reiniger-Werke AG from 1937 to 1955, the director of the Institute for Electron Microscopy of the Fritz Haber Institute from 1957 to 1974, and a lecturer at Technical University in Berlin from 1949 to 1971. (See also Physics.)