This is the original field from which radiology developed, and is probably still the most commonly employed form of radiology.  X-rays can be either still images or "movies," and can often be done quickly.  They are frequently used to complement other kinds of radiology imaging.

The films created by X-rays show different features of the body in various shades of gray.  The gray is darkest in those areas that do not absorb X-rays well; the grays are lighter in dense areas (like bones) that absorb more of the X-rays.  Some X-ray exams improve visibility by using contrast, a range of substances which may be introduced into the patient by swallowing, injection, or enema.