In 1985, a German physicist named William Roentgen discovered x-rays by mistake.  Roentgen was conducting an experiment on the flow of electricity through gases when he saw a fluorescent screen near his experiment start to glow.  He concluded that the glow was caused by unknown rays given off in his experiment.  He called the radiation X rays because of its unknown nature.  He discovered that the rays could penetrate through wood, paper, and human skin.  Roentgen placed his hand between the rays and the screen and could actually see his bone.  He concluded that the rays could penetrate dense materials more effectively than less dense materials.  He was able to take the first x-ray photograph with a photographic plate because it was sensitive to x-rays. 

The method that Roentgen used to produce an x-ray is the same method that medical professionals use today.  An x-ray detector collects photons of light from the x-ray, creating a silhouette picture.  Before the patient receives an x-ray, the doctor will apply a film to the area being observed.  The x-ray light is actually shot through the body to capture a picture of the bone.  X-rays are used to detect broken bones, tumors or other diseases in the body.