This lecture covers the synthesis of phosphoinositides from phosphatidylinositol, their crucial roles in cell signaling and membrane trafficking, and the dynamic equilibrium maintained by phosphoinositide kinases and phosphatases. It also discusses the regionalization of phosphoinositide metabolism, the diverse phosphoinositide enzymes, and the impact of phosphoinositides on organelle-specific recruitment of proteins. Furthermore, it explores the lipid metabolic crossroad of PtdIns(4)P, including its abundance in the Golgi complex, its role in lipid compartmentalization, and its involvement in sphingolipid metabolism. The lecture concludes with key messages on the production of ceramide, synthesis of sphingomyelin and glycosphingolipids at the Golgi, and the diverse functions of phosphoinositides.