The cell membrane, also referred to as the plasma membrane, is made of phospholipid molecules organized in a bilayer. Phospholipid molecules have a characteristic hydrophilic head, which contains a negatively charged phosphate group, and a hydrophobic tail, which consists of two fatty acid chains attached to the head. The contractile force exerted by the acto-myosin network divides one eukaryotic cell into two. A ring-like structure made of actins and myosins known as the contractile ring forms and constricts so to make a membrane bottleneck in the mother cell. Given that the interior of the cell consists mostly of water, one may try to describe the whole cell as a liquid drop; the cell membrane may be modeled separately or treated simply as a liquid-medium interface. An alternative interpretation of the existence of two regimes postulates two types of membrane wrinkles, the weakly and the strongly crosslinked ones.