Wilhelm Konrad von Roentgen (1845-1923), professor of physics at the University of Wurzburg, Germany, was working late on the night of November 3, 1893, after all his assistants had left the laboratory. He noticed that a fluorescent surface near a cathode-ray tube was luminous, even though shielded from the direct light of the tube, which made him realize that invisible radiation could pass through substances that would block ordinary visible light. Roentgen named his find X-strahl (which in English is X-ray), the X representing an unknown quantity.
In 1901, Roentgen became the first Nobel Prize winner in physics. Roentgen’s discovery of the electromagnetic rays of very short wavelength was invaluable in medicine, science, and the arts because they could penetrate human flesh as well as various thicknesses of many other things. The X-ray is possibly the medical profession’s most important and useful tool in the diagnosis and cure of disease. Roentgen reportedly made no personal profit through his remarkable discovery.