Breathing is the process of inhaling air rich in oxygen and exhaling air rich in carbon dioxide. Inhalation is taking air into the body through the nose and mouth, while exhalation is releasing air from the lungs through the mouth and nose. Air travels through the windpipe into the lungs, where gas exchange takes place in tiny air sacs called alveoli in the lungs. Oxygen passes from the alveoli into the bloodstream, while carbon dioxide passes from the bloodstream into the alveoli and is then exhaled.