ABSTRACT
Natural fluorescence emanating from a material was discovered by W. Röntgen (Roentgen) and originally called Röntgen rays. It was used to see the bones in the hand and soon was applied to many other objects to "see inside." He was working with cathode ray studies at the time, but the phenomenon was entirely different, although with many similarities. W. Crookes observed X-rays earlier but didn't realize what he had seen. Later, in 1896, A. H. Becquerel discovered radioactivity.
