Marie Curie was a pioneering physicist and chemist who conducted groundbreaking research on radioactivity. She was the first woman to win a Nobel Prize and the only person to win Nobel Prizes in two different scientific fields (Physics in 1903 and Chemistry in 1911). Her work led to significant advancements in the understanding of radioactivity, and she discovered the elements polonium and radium. Curie's research has had a profound impact on science and medicine, particularly in the development of X-ray machines and cancer treatments.