Growing numbers have sought out acupuncturists for chronic health problems -- when conventional medicine either hasn't worked nor has answers. According to the 2002 National Health Interview Survey, an estimated 8.2 million American adults have used acupuncture -- an impressive number considering only an estimated 2.1 million American adults had used acupuncture in the year before. Recent advances in technology have helped unlock the biological mysteries of this 2,500-year-old medical practice. The NIH and World Health Organization have both given formal approval of certain uses of acupuncture.