History of X-rays
X-rays were discovered in 1895 by Wilhelm Conrad Röentgen, a professor at Würzburg University in Germany. According to the Nondestructive Resource Center’s “History of Radiography” Web page, Röentgen noticed crystals near a high-voltage cathode-ray tube exhibiting a fluorescent glow, even when he shielded them with dark paper. Some form of energy was being produced by the tube, and it was penetrating the paper and causing the crystals to glow. Röentgen called the unknown energy “X-radiation.” Experiments showed that this radiation could penetrate soft tissues but not bone, and would produce shadow images on photographic plates.
For this discovery, Röentgen was awarded the very first Nobel Prize in Physics, in 1901. During World War I, X-rays were already being used for medical purposes.