First nuclear fission

On 14 December 1938 at Berlin’s Kaiser Wilhelm Institute, physicists Otto Hahn and Fritz Strassmann accidentally produce the first nuclear fission, laying the cornerstone for development of the atomic bomb. Shortly afterward scientist Lise Meitner, a friend of both researchers, publicizes the discovery.  Later, because of her Jewish heritage, Meitner must emigrate to Sweden.

Source: Forschungsneutronenquelle Heinz Maier-Leibnitz Otto Hahn's working place: the experiment arrangement for the first nuclear fission