The most abundant lipid in cell membranes is phospholipids. These molecules form a bilayer that serves as the structural foundation of cell membranes, effectively creating a barrier between the internal and external environments. Phospholipids consist of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails, facilitating the unique properties of cell membranes, such as fluidity and selective permeability. Their arrangement is crucial for various cellular processes, including cell signaling and transport of molecules.