(Left) This photo provided by Australian Synchrotron and the National Gallery of Victoria, shows an image discovered with X-ray fluorescence microscopy, beneath Edgar Degas' Portrait of a Woman. (Right) Degas' painting Portrait of a Woman. Australian Synchrotron and the National Gallery of Victoria via AP hide caption

toggle caption Australian Synchrotron and the National Gallery of Victoria via AP

Who's there? A radiologist studies digital X-rays in a viewing room at what is now called the Walter Reed National Military Medical Center in Bethesda, Md. Seth Rossman/U.S. Navy hide caption

toggle caption Seth Rossman/U.S. Navy