1. Phospholipids: These are the primary building blocks of the membrane. They form a phospholipid bilayer - two layers of phospholipids with their hydrophilic (water-loving) heads facing outwards towards the watery environment inside and outside the cell, and their hydrophobic (water-fearing) tails facing inwards. This structure forms a barrier that controls what can pass through the membrane.

2. Proteins: These are embedded within the phospholipid bilayer and perform various functions. Some proteins act as channels or transporters to facilitate the movement of specific molecules across the membrane. Others act as receptors to bind to signaling molecules, triggering responses inside the cell.

While these are the main components, other molecules like cholesterol are also present in the cell membrane, contributing to its fluidity and stability.