Actin polymerization is fundamental to many cellular activities, including motility, cytokinesis, and vesicle traffic. Actin dynamics must be tightly regulated so that cells execute a response appropriate to need, which is achieved through coordination of the functions of a molecular toolkit of proteins and phospholipids. Among the latter, phosphoinositides have a particularly important role, and PI(4,5)P₂ (phosphatidylinositol 4,5-bisphosphate) generates distinct phenotypic outcomes such as actin comet formation and membrane ruffling. New evidence reveals that it is not just the production of PI(4,5)P₂ that is important in determining outcome, but that changes in the abundance of other phosphoinositides also play a role.