When she was older, her husband died in 1906 in a car accident. When he died, she took over as the Chair of Physics. She started a radiology unit, which one million soldiers passed through. She started helping during World War One. She died at the age of 66, July 4, 1934. She had leukemia, which was caused by too much exposure to radium. She always slept with a sample of radium on her nightstand, which she didn't know wasn't good for her health. She is now buried at the famous dome, the Pantheon, in Paris. Her books and papers were too radioactive, so they are stored in lead boxes. She is best known for the theory of radioactivity.