Breathing, also called respiration, is the process by which living beings exchange gases with the external environment. There are three main types of breathing: abdominal breathing, which is the most common and involves breathing into the abdomen; costal breathing, which involves filling the middle region of the chest; and clavicular breathing, which involves the clavicle or collarbone region. There are also several breathing exercises described, including deep breathing to calm down after stress, diaphragmatic or abdominal breathing which focuses on abdominal breathing, and full breathing which combines deep and abdominal breathing into one technique.