The masseter muscle is one of the four muscles of mastication (chewing). It extends from the zygomatic arch to the lower border of the mandible. In some people, the muscle is so well developed that it makes the lower jaw look very broad and can give a 'square' appearance to the face. With appropriate treatment, the muscle mass can be reduced without impairing the ability to chew. These treatments are becoming increasingly popular in Asia (Asians suffer more frequently from an enlarged masseter).