The cell membrane consists of two molecular structures: Proteins and Phospholipids. The proteins are used for cell recognition, communication, and for moving substances in and out of the cell. The vast majority of the cell membrane is made of phospholipids. A phospholipid consists of a phosphate "head" with two long "tails" of lipids. The phosphate head is "hydrophilic" meaning it is attracted to liquid environments. The lipid tails are "hydrophilic" meaning they move away from liquid environments. The cell membrane is two layers of these phospholipids. The outer layer has the heads pointing towards the liquid environment outside the cell. The inner layer has the heads pointed inwards towards the liquid interior of the cell. The tails are on the inside of this layer, in a dry environment.
Outside environment
OOOOOOOOOOOOOO <- Phosphate heads (Hydrophilic)
l ll ll ll ll ll ll ll ll ll ll ll ll ll l
Inside the bilayer
l ll ll ll ll ll ll ll ll ll ll ll ll ll l <- Lipid tails (Hydrophobic)
OOOOOOOOOOOOOO
Cell interior