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
Marie Curie chosen field in Poland, but she was denied a place at Kraków University because she was a woman. A letter from Pierre Curie convinced her to return to Paris to pursue a Ph.D. At Skłodowska's insistence, Curie had written up his research on magnetism and received his own doctorate in March 1895; he was also promoted to professor at the School. A contemporary quip would call Skłodowska, "Pierre's biggest discovery." On 26 July 1895 they were married in Sceaux (Seine); neither wanted a religious service. Curie's dark blue outfit, worn instead of a bridal gown, would serve her for many