Our phosphol lipids cannot actually jump back and forth. So we only have lateral or sideway motion. We do not have vertical motion because if the vertical motion was to actually take place, that would result in very high electrostatic repulsion. And so, because we don't want to have high electrostatic repulsion, we don't want to waste so much energy, our phospholipids will only move back and forth and will not jump vertically, as shown. And this type of motion, a constant fluid like motion of our phospholipid bilayer, is known as the fluid mosaic model. Now, the last part that I want to discuss is an important part of our phospholipid bilayer, that is our cholesterol.