Lise Meitner with Otto Hahn. Meitner discovered nuclear fission.
In 1939 an English physicist received a cable from Sweden, and it seemed to make no sense. The clouds of WW-II were gathering over Europe, and here came a chatty cable about somebody he'd never heard of named Maud Ray Kent. Now who was Maud Ray Kent!
But he knew the woman who sent the wire: she was a noted physicist named Lisa Meitner. She had a doctorate from Vienna, and in 1908 she'd gone to work for Max Plank in Berlin. Her close colleague there was another young physicist named Otto Hahn. Their association stretched into a 60-year friendship.
Women weren't allowed to work in the laboratory, so Hahn and Meitner had created their own lab in a carpenter's shop. They worked on nuclear fission until WW-I. Then Meitner joined the Austrian army as an X-ray technician. But she kept working with Hahn whenever they both could get away on leave. By 1918 they'd created a new element they called protactinium. It is a part of the periodic table.
By war's end, Germany had lost a whole generation of males, and opportunities had briefly improved for women. Meitner was made head of the physics department at the Kaiser Wilhelm Institute in Berlin. There she and Hahn went to work on a and b radiation. Sixteen years later they were bombarding heavy elements with fast neutrons. It was finally Meitner who realized what enormous energy was released when uranium fissioned into barium.
John Lienhard at the University of Houston, Engines of Our Ingrenuity: http://www.uh.edu/engines/epi305.htm