Hypnosis began in ancient civilizations as part of religious rituals involving meditation and drumming. Franz Mesmer was an early pioneer of hypnosis in the late 18th century, believing that magnetic fluid in the body caused illness. He treated patients using hypnosis in an iron tub. While hypnosis involves a trance-like state, the subject remains aware and can respond to suggestions. Effects of hypnosis can vary but include relaxation, detachment, or actions feeling outside conscious control. Hypnosis is used to treat various medical conditions from pain to nausea, but stage hypnosis carries risks like misinterpreted suggestions and physical injuries.