Andrew Huberman· PhD
As the lungs expand, basically, it's like a balloon that you would pull apart. The pressure inside that balloon drops and the air will flow into the balloon. So we expand, put pressure on the lungs to pull it apart, that lowers the pressure in the air sacks called alveoli and air will flow in because pressure outside the body is higher than pressure inside the body when you're doing this expansion, when you're inhaling.