X-ray of a male baby, from the Institute of Anatomy at University College, London. In 1895, German physicist Wilhelm Konrad Roentgen (1845-1923) discovered X-rays - the 'X' signified their unknown origin. X-rays travelled in a straight-line and passed through card, but could be detected by a photographic plate or fluorescent screen. Later, he found that they were able to pass through flesh and take photographic images of bones inside the body.
© Royal Photographic Society / Science & Society Picture Library