Phosphoinositides, the phosphorylated products of inositol phospholipids, play critical regulatory roles in cell physiology. Through interactions mediated by their cytosolically exposed and differentially phosphorylated head groups they help control membrane-cytosol interactions. As each of the 7 phosphoinositide species has a unique subcellular localization, they also help define specific interaction ofdifferent membranes. The elucidation of phosphoinositide functions greatly benefit from methodologies to manipulate their concentrations within specific membranes with high spatial and temporal precision. The talk will discuss the useof the blue light-dependent CRY2-CIB1 dimerization modules (1,2) to rapidly and reversibly relocate phosphoinositide-metabolizing enzymes to control specific phosphoinositide dependent reactions within cellular membranes.