phospholipids
You can see a model of the cell membrane in Figure below . The molecules that make up the cell membrane are mainly phospholipids. There are two layers of phospholipids. They are arranged so the lipid tails are on the inside of the membrane. They make the interior of the membrane hydrophobic, or "water fearing". The lipid heads point toward the outside of the membrane. The make the outer surfaces of the membrane hydrophilic, or "water loving". Different types of proteins are embedded in the lipid layers. The proteins are needed to help transport many substances across the membrane.