During plant cell division, the thin cell plate formed during cytokinesis is restructured into the cell walls of daughter cells. As the young cell grows, more and more cellulose is added to the cell wall. Cellulose synthase or CESA is a multimeric enzyme that uses cytosolic UDP-glucose to spin out cellulose chains on the ECM face of the plasma membrane. CESA moves on microtubule-defined channels just under the plasma membrane, to orient the newly deposited cellulose chains. The nascent cellulose chains self-assemble to form microfibrils. The distal ends of the stiff microfibrils integrate into the cell wall while the elongating proximal ends push CESA along microtubule tracks. As the cell expands, the microtubules rearrange to control the orientation of new cellulose microfibrils and determine cell shape.