Lipid droplets (LDs) store lipids for making cellular membranes and for metabolic energy, but it’s unclear exactly how they’re made. A team led by Dr. Robert Farese, Dr. Tobias Walther, and Dr. Jeeyun Chung (HMS/HSPH) discovered that a complex of lipid droplet assembly factor 1 in interaction with seipin, an endoplasmic reticulum (ER) protein, is the core protein machinery that drives the formation of LDs and determines where they form in the ER. Appearing in Developmental Cell, the work could have implications for common metabolic diseases and industrial applications, such as production or biofuels.