These lipid layers are made up of a number of fatty acid building blocks. The fatty acid that makes up this membrane has two different parts to it- a small water loving head- hydrophilic head. Hydro stands for water and philic means liking or loving. The other part of this fatty acid is a long water-repelling or water hating tail.

This tail is hydrophobic- Hydro stands for water and phobic means fear. The plasma membrane is arranged in such a way so that the tails face each other on the inside and the heads face towards the outside of the membrane.