Now, once our voltage of the membrane decreases back to the threshold value of about negative 45 millivolts, some of the inactivated sodium channels will begin to recover. So they will begin to close, but now they're no longer inactivated. And this part will become important when we'll discuss the absolute refractory period and the relative refractory period. Now, at this point, our permeability of the membrane to potassium is actually higher than normal. And this is exactly what causes our voltage of the cell to drop below the resting voltage in this period, when our voltage of the membrane drops slightly below the resting membrane potential. This is known as the hyperpolarization period.