Inhalation (also known as inspiration) is the movement of air from the external environment, through the air ways, into the alveoli during breathing.Inhalation begins with the onset of contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's Law. This negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. Air enters, inflating the lung through either the nose