Acupuncture is a component of the health care system of China that can be traced back at least 2,500 years. The general theory of acupuncture is based on the premise that there are patterns of energy flow (Qi) through the body that are essential for health. Disruptions of this flow are believed to be responsible for disease. Acupuncture may, it has been theorized, correct imbalances of flow at identifiable points close to the skin. The practice of acupuncture to treat identifiable pathophysiological (disease) conditions in American medicine was rare until the visit of President Richard M. Nixon to China in 1972. Since that time, there has been an explosion of interest in the United States and Europe in the application of the technique of acupuncture to Western medicine. Acupuncture is a family of procedures involving stimulation of anatomical locations on or in the skin by a variety of techniques. There are a variety of approaches to diagnosis and treatment in American acupuncture that incorporate medical traditions from China, Japan, Korea, and other countries. The most thoroughly studied mechanism of stimulation of acupuncture points employs penetration of the skin by thin, solid, metallic needles, which are manipulated manually or by electrical stimulation.