How do phospholipid molecules lead to the compartmentalization of a cell?

The phospholipid molecules will spontaneously assemble into a phospholipid bilayer when they are added to an aqueous environment that consists mostly water. Phospholipids form all membrane in the cell, the membrane is separate inside from the outside of an organelle, that is phospholipid membranes are what form the compartments that we know of as organelles.