Marie Curie, Polish-born French physicist, 1931.

Marie Curie, Polish-born French physicist, 1931. Marie (1867-1934) and her husband Pierre Curie continued the work on radioactivity started by Henri Becquerel. In 1898, they discovered two new elements, polonium and radium. Marie did most of the work of producing these elements, and to this day her notebooks are still too radioactive to use. She went on to become the first woman to be awarded a doctorate in France, and continued her work after Pierre's death in 1906. In 1903 the Curies shared the Nobel Prize for Physics with Becquerel. Marie won a second Nobel Prize, for chemistry, in 1911. (Photo by Oxford Science Archive/Print Collector/Getty Images)