So the process of inhalation is an active process because it requires using ATP for muscle contraction. Now, as the diaphragm begins to contract, it begins to flatten out. So it moves in the following general direction. Now, the diaphragm is actually connected to the chest cavity, our thoracic cavity. And as the diaphragm flattens down, it increases the space inside our chest cavity. It increases the volume inside that chest cavity.