Adipocyte differentiation-related protein (ADFP) is found on the surface of lipid droplets in most mammalian cell types. In mammals, lipid droplets are most abundant in adipose tissue, where stored triacylglycerol (TAG) provides the primary energy reserve for the organism. Lipid droplets in steroidogenic cells contain cholesteryl esters used in the synthesis of steroid hormones. Most other mammalian cells contain smaller lipid droplets, whose function remains unclear.