And as they move into the cell, they carry positive charge into the cell. And as they carry positive charge, that increases the positive charge on the inside of the cell compared to our outside. So we see this increase as shown by this curve. Now, when we reach about negative 40 millivolts. When it becomes greater than negative 40 millivolts, we also have the opening of these special Ltype calcium channels, and we'll see what those are in just a moment. So as these sodium channels, as these sodium ions rush in, they create a positive charge on the inside and a negative charge on the outside.