Wilhelm Conrad Röntgen (1845-1923), a German physicist who received the first Nobel Prize for Physics in 1901 for his discovery of the X-ray in 1895. This discovery initiated a new era of modern physics and would revolutionize the practice of diagnostic medicine. In 1895, while experimenting with electric current flow in a partially evacuated glass tube (cathode-ray tube), Röntgen observed that a nearby piece of barium platinocyanide gave off light when the tube was in operation. Further investigation revealed that paper, wood, aluminum, and many other materials were transparent to this new form of radiation, which also affected photographic plates. Röntgen took the first ever X-ray photographs of the interiors of metal objects and of the bones in his wife's hand. Like Pierre Curie several years later, he refused on moral grounds to take out any patents related to his discovery. The Röntgen (symbol 'R') is a unit of dosage for X-rays or gamma radiation. Natural background is around 10 mR per hour; 500 R over 5 hours is lethal to humans.