Inositol with all 6 hydroxyl groups phosphorylated (the molecule depicted here, termed inositol hexakisphosphate or IP₆) is the substrate for inositol hexakisphosphate kinase 1 (IP6K1), which adds yet another phosphate group to this molecule in order to create inositol pyrophosphates. In a manner not well understood, knocking out the IP6K1 enzyme in mice severely decreases the accumulation of polyphosphate in platelet dense granules, with consequences for platelet function in both hemostasis and thrombosis. Professional illustration by Marie Dauenheimer.