Now, let's suppose we're taking our normal breath. So we're basically right here. Now, eventually, when we're taking our normal breath, let's suppose we actually want to forcefully exhale all the remaining air in our lungs. So we take a breath and at this position we begin to forcefully exhale the remaining air. And at the maximum point of the forceful exhalation, we're going to be at this location and the distance from this purple line all the way to the top. This distance here is known as the vital capacity.