Radiography is the examination of a specimen or any part of the body, usually for diagnostic purposes, by means of roentgen rays, recording the image on a sensitized surface such as photographic film.
X-rays are a form of electromagnetic radiation, just like visible light. An x-ray machine sends individual x-ray particles, called photons, that pass through the body and the images are recorded by special film or a computer. Bone and structures that are dense will block most of the x-ray particles, appearing white in the image. Metal and contrast media or special dye will also appear white. Structures containing air will be black and muscle, fat, and fluid will appear in the image as shades of gray.