The cell wall is a tough extracellular matrix that surrounds plant cells and is responsible for many of the unique features of a plants lifestyle. The cell wall is primarily made up of cellulose, which is the most abundant macromolecule on Earth. The cell wall provides structural support to the plant cell and acts as the first line of defense when the plant encounters pathogens. It also provides flexibility to support cell division, a biochemical scaffold that enables differentiation, and a pathological and environmental barrier that defends against stress. The tensile strength of the cell wall allows plant cells to develop turgor pressure, which is important for maintaining the shape of the cell and for supporting the plant. The cell wall is assembled in place, and precursor components are synthesized inside the cell and then assembled by enzymes associated with the cell membrane. The composition of the cell wall depends on the cell type, and the primary cell wall is the focus of most research on the molecular architecture that underlies its remarkable combination of strength, resilience, and plasticity.