Inositol phosphates have been recognized as biologically relevant molecules since the identification in the early 20th century of inositol hexakisphosphate (IP6, also known as phytic acid) as an abundant constituent of plants that makes up their principal phosphate store. Interest in these substances escalated with the discovery in the mid-1980s of IP3 [inositol 1,4,5-trisphosphate] as a second messenger that releases calcium from intracellular stores. Mammalian cells produce higher-order inositol phosphates (IP4, IP5, IP6, etc.) whose roles in physiology is mostly obscure. Out of six major inositol phosphate generating enzymes (IP3kinase, IPMK, IP5kinase, IP6k1, IP6K2, and IP6K3), IPMK may be the most important, as deletion is embryonic lethal for mice. The inositol phosphate kinase function of IPMK is conserved from plants to mammals, where it converts IP3 to IP4 and IP4 to IP5. In mammals, IPMK also possesses phosphatidylinositol 3-kinase (PI3K) activity, generating phosphatidylinositol (3,4,5)-trisphosphate (PIP3), a second messenger that promotes cellular growth and cancer progression. We are interested in exploring the physiological importance of IPMK and inositol signaling in cell and animal models.