It leaves the cell of potassium, and this extends our depolarization period and is known as our plateau phase. So this is our plateau phase because we essentially reach a point on the action potential where the membrane potential is not changing, it remains around zero millivolts. Now, some people say that this is an extension of depolarization, because what depolarization does is it basically maintains a positive concentration on the inside of the cell. And that's exactly what we see on this diagram. Now, other people say that this is our depolarization shown in red. This is our early repolarization, because repolarization means we're basically in the process of returning our membrane voltage to normal.