Now, the tidal volume is the portion between this top line and this bottom line. So this is our tidal volume. And so these fluctuations basically describe the normal breathing rate. So we essentially inhale and then we exhale and we exchange about 500 air every time we take that breath. Now, what exactly is the maximum amount of air that the lungs can actually store? This is called the total lung capacity and it's the distance between this maximum point and the zero line.