Abstract: In eukaryotes, cell polarity emerges from the complex interplay between plasma membrane and cytoplasmic molecules, most notably phosphatidylinositol phosphate (PIP) lipids, lipid modifying enzymes, small GTPases, and the actin cytoskeleton. In many cases, competition between lipid kinases and phosphatases underlies the production of PIP lipids that become asymmetrically distributed across the plasma membrane. Although many of the enzymes that regulate PIP lipid synthesis in vivo have been identified, questions concerning how PIP lipid phosphorylation reactions are rapidly turned ON and OFF remain unanswered. The Hansen lab has taken a reductionist approach to biochemically reconstitute minimal sets of signaling molecules that control PIP lipid phosphorylation at the plasma membrane. The knowledge gained from our biochemical analysis has provided new insights concerning how lipid modifying enzymes regulate the formation of transient, polarized, and oscillatory PIP lipid signaling reactions in living cells.