There is a certain voltage difference between the inside and the outside of the cell, and this is known as the resting membrane potential. So, once again, the resting membrane potential is the voltage difference or the electric potential difference between the inside and the outside of a neuron that is not generating any action potential. So let's begin by looking at the following diagram. So this diagram describes the relative concentrations of sodium ions and potassium ions on the outside and inside of the neuron cell membrane. So this is the phospholipid bilayer, the membrane of the neuron, let's say, found on the exxon hillock where the action potential is generated. But, of course, no action potential is being generated in this particular case.