Marie Curie theory of "radioactivity" (a term that she coined), techniques for isolating radioactive isotopes, and the discovery of two elements, polonium and radium. Under her direction, the world's first studies into the treatment of neoplasms were conducted using radioactive isotopes. She founded the Curie Institutes in Paris and in Warsaw, which remain major centres of medical research today. During World War I, she developed mobile radiography units to provide X-ray services to field hospitals. While a French citizen, Marie Skłodowska Curie, who used both surnames, never lost her sense of Polish identity. She taught her daughters the Polish language and took
Pierre Curie in honor of Pierre, Marie, or both. In the late nineteenth century, Pierre Curie was investigating the mysteries of ordinary magnetism when he became aware of the spiritualist experiments of other European scientists, such as Charles Richet and Camille Flammarion. Pierre Curie initially thought systematic investigation into the paranormal could help with some unanswered questions about magnetism. He wrote to his fiancée Marie: "I must admit that those spiritual phenomena intensely interest me. I think in them are questions that deal with physics." Pierre Curie's notebooks from this period show he read many books on spiritualism. He did not attend