Traditional Chinese medicine is based on the principles of yin and yang balance and the flow of qi energy through energy channels. Diagnosis involves examining the pulse, tongue, questioning the patient about their symptoms, sleep, diet, etc. Illnesses are believed to be caused by imbalances among the five elements of wood, fire, earth, metal, and water, which relate to different organs. Acupuncture and herbal remedies are used to treat energy imbalances and restore balance. Qigong exercises also aim to promote the flow of qi energy. Famous early practitioners included Bian Qiao, Hua Tuo, and Sun Simiao who made important contributions to diagnosis, treatments, and recording knowledge of Chinese medicine.