Invented in 1913, this X-ray tube was more controllable and consistent than earlier types. The X-ray or 'new' photography caused a sensation when it was discovered by German scientist Professor Roentgen (1845-1923) in 1895. In 1895, as Professor of Physics at the University of Würzburg, Rontgen was experimenting with a Crookes tube, invented in 1875. He noticed that when cathode rays struck the end of a discharge tube, rays of a new kind were emitted, capable of penetrating matter. He had discovered X-rays. X-rays are emitted whenever fast-moving electrons are stopped in their tracks. Later X-ray tubes, like the one shown here, used a cathode filament to produce a greater output of X-rays.