It is with much hesitancy that I venture to write a preface to this book. She once chided me, in her gentle way, for an article in which I had stated facts with some feeling--although the facts praised her. "In science," she said, "we should be interested in things, not persons." Madame Curie is the most modest of women. It is only after long persuasion that she has consented to record the autobiographical notes contained in this book. Still, so much has been left unsaid, uninterpreted, that I feel an obligation to say a word toward a fuller understanding of this great and noble character. In 1915 I wrote in my editor's suggestion book: "Greatest woman's story in the world--Marie Curie, discoverer of radium." For the next four years scarcely any writer of prominence went abroad without a commission from me to bring back the story of Madame Curie. Always they returned with the report: "She was not to be found," or "She was at the front somewhere," or "She won't see journalists." My own letters to Madame Curie brought no reply. I did not know then that great bags of mail from all parts of the world lay piled up in her laboratory where there was no secretary, while Madame Curie with her X-ray apparatus was at the front, relieving suffering and saving lives. In May, 1919, another mission took me to Paris and I resolved to see Madame Curie myself. My friend, Stéphane Lauzanne, Editor-in-Chief of _Le Matin_, said: "Give it up. Become interested in something else; she will see no one. She does nothing but work." I began to ask questions. "She is very simple and exceedingly retiring," said Lauzanne. "Few things in life are more distasteful to her than publicity. Her mind is as exact and logical as science itself. She cannot accept or understand exaggerations and inaccurate quotations. She cannot understand why scientists, rather than science, should be discussed in the press. There are but two things for her--her little family and her work. "After the death of Pierre Curie, the faculty and officials of the University of Paris decided to depart from all precedent and appoint a woman to a full professorship at the Sorbonne. Madame Curie accepted the appointment and the date was set for her installation. "It was the history-making afternoon of October 5th, 1906. The members of the class which had formerly been instructed by Professor Pierre Curie were seated in one group. "There was present a large crowd--celebrities, statesmen, academicians, all the faculty. Suddenly through a small side door entered a woman all in black, with pale hands and high arched forehead. The magnificent forehead won notice first. It was not merely a woman who stood before us, but a brain--a living thought. Her appearance was enthusiastically applauded for five minutes. When the applause died down, Madame Curie bent forward with slightly trembling lips. We wondered what she was about to say. It was important. It was history, whatever she said.