Pierre and Marie Curie, French physicists, preparing to go cycling. Polish-born Marie Curie and her husband Pierre 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 they shared the Nobel Prize for Physics with Becquerel. Marie won a second Nobel Prize, for chemistry, in 1911. (Colorised black and white print). Artist Unknown. (Photo by The Print Collector/Getty Images)