The membrane is organised as a bilayer, with hydrophilic heads interacting with the watery contents of the cytoplasm and the surroundings, and the hydrophobic tails pointing inwards and interacting with each other. This is a low-energy, physically ‘comfortable’ state: despite its ordered appearance, the formation of lipid bilayers actually increases overall entropy by releasing energy as heat into the surroundings.
To understand this, remember that the second law says, "the total, overall entropy of a set of participating systems always increases."
