Mechanisms of LD size control and spatial organization. (A) Model of LD biogenesis as it is affected by TG biosynthesis. Low rates of TG synthesis in the ER results in small, sparse LDs. (B) Elevated TG biosynthesis in the ER drives both more LD formation as well as LD growth as TG is deposited into LDs for storage. (C) Depiction of Cidec/Fsp27-mediated LD–LD fusion.