Plant cells have a complex vacuolar system in which storage and lytic vacuoles may coexist in the same cell. This arrangement presumably is required to protect stored products from environments in which they would be degraded; however, little is known about how these functionally distinct compartments are generated and maintained by cells. In an attempt to develop probes that would identify distinct vacuole types, Jauh et al. have utilized antibodies specific for different tonoplast intrinsic proteins (TIPs) that are abundant in vacuole membranes. As they show on pages 1867-1882, the presence of certain TIP isoforms correlates with different vacuolar functions, providing an initial biochemical definition of vacuole types. The cover shows a cell whose vacuoles are immunofluorescently labeled with antibodies against delta-TIP (in green), gamma-TIP (in blue), and aleurain, a vacuolar protease (in red). A distinct population of anti-delta-TIP- and anti-aleurainlabeled vacuoles appears in yellow.