What happens with your diaphragm?

When you breath in, the diaphragm contacts and the rib cage rises up. This expands the volume of the chest cavity. Because the chest cavity is tightly sealed, this creates a partial vacuum inside the chest cavity. Atmospheric pressure does the rest, filling the lungs as air rushes into the breathing passages. When the rib cage lowers and the diaphragm muscle relaxes, the pressure in the chest cavity becomes greater than atmospheric pressure and air rushes back out of the lungs.

Now you try and observe your diaphragm