Wilhelm Röntgen discovered X-rays in 1895.
On 8 November 1895, German physicist Wilhelm Conrad Röntgen noticed that a fluorescent screen glowed while he was experimenting with discharge tubes at the University of Würzburg. The tube was covered to block visible light, yet an unseen radiation still reached the screen. Because its nature was unknown, he called it X-radiation.
Röntgen investigated the rays intensively and demonstrated that they could pass through soft tissue more readily than bone. In December 1895, he produced an important early radiograph of his wife Anna Bertha’s hand. His report spread rapidly, and the discovery quickly transformed medical imaging.
The finding also inspired Henri Becquerel to investigate whether fluorescent materials emitted similar penetrating radiation. In 1896, Becquerel discovered spontaneous radioactivity in uranium salts. That connection makes 1895 an important starting point for the history of radioactivity, although X-rays are electromagnetic radiation produced by energetic electrons, not radioactive decay.