Inositol lipids phosphorylated at the 3-OH position, such as PtdIns(3,4)P2 and PtdIns(3,4,5)P3, play important roles in cell migration, cell proliferation and membrane trafficking. Generated by PI 3-kinases in response to various stimuli, these 3-phosphoinositides recruit proteins containing PH, PX or FYVE domains to specific membrane sites, where they can regulate downstream signalling. Phosphatases including PTEN then switch off signalling by removing the 3-phosphate group. To characterize 3-phosphoinositide signalling in Dictyostelium chemotaxis and phagocytosis, Cornelius Weijer and co-workers have used GFP-tagged contracts containing various different PH domains to monitor these phospholipids (see p. 6497). Their approach yields several unexpected results. For example, it shows that phagocytosis and chemotactic signalling both involve generation of PtdIns(3,4,5)P3 but only phagocytosis generates PtdIns(3,4)P2 – PTEN presumably converts PtdIns(3,4,5)P3 to PtdIns(4,5)P2 before PtdIns(3,4)P2 can be formed in chemotaxis. Perhaps the most interesting observation, however, is that PtdIns(3,4,5)P3-binding PH domains from different proteins exhibit different localization patterns – probably because of their different binding affinities. This indicates that a single 3-phosphoinositide-generating signal can generate distinct spatiotemporal biological outputs.