Cells signal through lipids produced by phospholipid and phosphoinositide metabolism that involves three enzymic processes: (i) ester and phosphodiester hydrolysis by phospholipases; (ii) monophosphate hydrolysis by phosphatases; and (iii) phosphorylation of hydroxy groups by kinases. Unregulated enzyme activity correlates with specific pathologies, which are specific targets for therapeutic intervention. Three categories of reagents developed at the University of Utah and at Echelon Biosciences permit monitoring of in vitro enzyme activity and spatiotemporal changes in intracellular lipid concentrations, and identification of lipid-protein interactions.