Throughout World War I, Marie Curie, with the help of her daughter Irène, also involved in scientific activities, devoted herself to the development of medical application of X-radiography.
She pushed for the use of mobile radiography units, which were popularly known as "Little Curies" ("petites Curies"), and which played a significant role in the diagnosis of wounded soldiers. These units were powered by tubes of radium emanation, which derived from the material she purified.
Headed by Marie, the laboratory was the first in the world to perform experiments on the treatment of cancer cells with radiant substances.
Marie realized that large quantities of radioactive substances needed to be accumulated in order to treat illnesses as well as to supply the research works with sufficient material. To achieve this, she visited several countries.
Her trip to the United States in 1921 was an absolute triumph as President Harding presented her with 1 g of pure radium bought on the funds raised by the American women.