Acupuncture needles. A selection of needles used in Chinese acupuncture. The needles vary in length and thickness depending on their use. Acupuncture involves the insertion of fine metal needles at specified points into the skin of a patient. The needles can be vibrated, heated or have a small electric current applied. The point of insertion is governed by the symptom. Acupuncture needles are thought to activate sensory nerves, promoting the brain to produce endorphins (natural analgesics). In western culture, acupuncture is increasingly used in complementary medicine for relief of pain or the withdrawal symptoms of addiction. Photographed in Korea.