Cells store extra membrane along pits and protrusions in the cell surface. But how cells regulate those membrane stores is not well understood. ASCB members Lauren Figard, Anna Marie Sokac, and colleagues at the Baylor College of Medicine monitored membrane supply and demand in Drosophila embryos. They found that the process of exocytosis adds membrane and promotes F-actin protrusions that organize the membrane into microvilli. Then during cell division the furrow ingression promotes microvillar F-actin disassembly, which allows the membrane to unfold as one cell becomes two. The work was published in Developmental Cell.