<< Hydrophobicity | Self-assembly
Self-assembly occurs due to the thermodynamics, if the phospholipids are in a water (or other polar solution) the tails will want to be 'away' from the solution. The could all go to the top (like oil on water), or they could have the tails point toward each other. With the tails pointing toward each other, this could form 2 different formations.
First would be a micelle which would like like a ball with the phospholipid heads on the outside and the tails pointing together like this or in the form of a lipid bilayer: