Marie Curie was a pioneering Polish and naturalized-French physicist and chemist who conducted groundbreaking research on radioactivity. She was the first woman to win a Nobel Prize, the first person and only woman to win the Nobel Prize twice, and the only person to win the Nobel Prize in two different scientific fields. Alongside her husband, Pierre Curie, she discovered the elements polonium and radium, and her work led to the isolation of pure radium and the development of mobile X-ray units during World War I.