And at that particular point, when the intralural space has a pressure that is lower than the pressure inside the intrapulmonary area, then our air will begin to move down its gradient, down the pressure gradient from a high pressure to a low pressure. So, in the same exact way that a marker or any other mass will always move down its potential gradient, gravitational potential gradient, from a high potential to a low potential, molecules, air molecules will also always move from a higher pressure to a low pressure. And that's exactly why when the diaphragm flattens down and when the external intercoastal muscles contract and expand the ribcage, that increases the volume and decreases the pressure inside the intraplural space. And that creates a pressure difference, also known as a pressure differential or negative pressure. And now our air molecules move from a high pressure from the outside to the inside into our lungs. Now, actually, I don't like using this term called negative pressure because it's misleading.