The lipid droplet (LD) is a unique multi-functional organelle that contains a neutral lipid core covered with a phospholipid monolayer membrane.The LDs have been found in almost all organisms from bacteria to humans with similar shape.Several conserved functions of LDs have been revealed by recent studies,including lipid metabolism and trafficking,as well as nucleic acid binding and protection.We summarized these findings and proposed a hypothesis that the LD is a conserved organelle.