On 8 November 1895, German physics professor Wilhelm Conrad Roentgen (1845-1923) worked in his darkened Wurzburg laboratory. His experiments focused on light phenomena and other emissions generated by discharging electrical current in highly-evacuated glass tubes. These tubes, known generically as "Crookes tubes," after the British investigator William Crookes (1832-1919), were widely available. Roentgen was interested in cathode rays and in assessing their range outside of charged tubes.
To Roentgen's surprise, he noted that when his cardboard-shrouded tube was charged, an object across the room began to glow. This proved to be a barium platinocyanide-coated screen too far away to be reacting to the cathode rays as he understood them. We know little about the sequence of his work over the next few days, except that while holding materials between the tube and screen to test the new rays, he saw the bones of his hand clearly displayed in an outline of flesh.
It is impossible for observers accustomed to modern imaging to gauge the mixture of wonder and disbelief Roentgen must have felt that day. When he immobilised for some moments the hand of his wife in the path of the rays over a photographic plate, he observed after development of the plate an image of his wife's hand which showed the shadows thrown by the bones of her hand and that of a ring she was wearing, surrounded by the penumbra of the flesh, which was more permeable to the rays and therefore threw a fainter shadow.
On 28 December 1895 Roentgen gave his preliminary report "Uber eine neue Art von Strahlen" to the president of the Wurzburg Physical-Medical Society, accompanied by experimental radiographs and by the image of his wife's hand. By New Year's Day he had sent the printed report to physicist friends across Europe. January saw the world gripped by "X-ray mania," and Roentgen acclaimed as the discoverer of a medical miracle. Roentgen won the first Nobel prize in physics in 1901.