Lise Meitner and Otto Hahn at the Kaiser Wilhelm Institute for Chemistry in Berlin (1928) In December 1938, the German chemist Otto Hahn discovered the nuclear fission of uranium at the Kaiser Wilhelm Institute for Chemistry in Berlin. He made this breakthrough after years of collaboration with Austrian physicist Lise Meitner, who had fled to Sweden on account of her Jewish heritage shortly before Hahn made his discovery. In January 1939, Meitner and Otto Robert Fritsch wrote the first physical-theoretical interpretation of the process.