To be able to see inside a living, breathing body must have seemed like science fiction to medical practitioners in 1896.

No wonder they all got so excited that year when German physicist Wilhelm Röntgen announced his discovery of x-rays. X-rays are high energy rays that pass though soft tissue to form an image on either a fluorescent screen or photographic film. Fewer rays pass through denser material, like organs and bones, so these areas appear lighter on photographic film. Now hospitals are moving to a filmless system, using digital images that are stored electronically.