November 8, 1895. Wilhelm Conrad Rontgen's discovery of X-rays happened accidentally as he conducted a test on cathode rays. He noticed a glow on a screen coated with chemicals. Rontgen called the rays that caused the glow X-rays. After conducting more experiments, Rontgen discovered that X-rays could pass through human flesh, but not harder substances such as bone. He also learned that they could be photographed. The discovery was hailed as a medical miracle. X-rays were first used on a battlefield during the Balkan War in 1897. Rontgen received the Nobel Prize in physics for his work, but never attempted to gain financially for his discovery.