Inhale exhale and... The title brings back memories from the 2000s😁😁 That's not what we wanted to tell you. One of these processes is active and the other is passive (let the muscles take part in it as well). The respiratory muscles - the diaphragm, the intercostal muscles, the abdominal muscles and the neck muscles - assist the inhalation. They expand the chest and simplify the process of expanding (and filling with air) lungs - it is an active process. Exhaling is a passive process, but it also involves muscles that are expiratory (exhalation muscles).