Practiced in China and other Asian countries for thousands of years, acupuncture is one of the key components of traditional Chinese medicine. In TCM, the body is seen as a delicate balance of two opposing and inseparable forces: yin and yang. Yin represents the cold, slow, or passive principle, while yang represents the hot, excited, or active principle. According to TCM, health is achieved by maintaining the body in a "balanced state"; disease is due to an internal imbalance of yin and yang. This imbalance leads to blockage in the flow (vital energy) along pathways known as meridians. Qi can be unblocked, according to TCM, by using acupuncture at certain points on the body that connect with these meridians.