Lipins are phosphatidic acid phosphatases that regulate de novo phospholipid synthesis and fat storage as triglycerides, and lipin dysfunction leads to metabolic disorders, including lipodystrophy and rhabdomyolysis. While lipins have been extensively studied at the cellular and physiological level, what has lagged behind is a molecular understanding of their function. The major mystery has been how the two essential regions called the N-Lip and C-Lip, which are located on opposite ends of the lipin protein molecule in humans, come together to form a functional enzyme. The first structure of a lipin (https://www.nature.com/articles/s41467-020-15124-z) revealed a surprising, but clear model for how the N-Lip and C-Lip collaborate to bind membranes and hydrolyze the membrane-lipid phosphatidic acid