Now, let's move on to cholesterol molecules. So, cholesterol molecules actually have a very special shape and that's because cholesterol molecules are actually steroid molecules. And what that means is they contain a four ring structure as shown in the following diagram. So cholesterol is a steroid, which means it is composed of four fused hydrocarbon rings. Now, on one side of those four rings, we basically have a tail that is hydrophobic. So this hydrocarbon chain, on the other side, we have a polar group.