Lipid droplets are composed of a neutral lipid core consisting mainly of triacylglycerols (TAGs) and cholesteryl esters surrounded by a phospholipid monolayer. The surface of lipid droplets is decorated by a number of proteins which are involved in the regulation of lipid metabolism. The first and best-characterized family of lipid droplet coat proteins is the perilipin protein family, consisting of five proteins. These include perilipin 1 (PLIN1), perilipin 2 (PLIN2/ ADRP), perilipin 3 (PLIN3/ TIP47), perilipin 4 (PLIN4/ S3-12) and perilipin 5 (PLIN5/ OXPAT/ LSDP5/ MLDP).  Proteomics studies have elucidated the association of many other families of proteins to the lipid surface including proteins involved in membrane trafficking, vesicle docking, endocytosis and exocytosis.  Analysis of the lipid composition of lipid droplets has revealed the presence of a diverse set of phospholipid species; phosphatidylcholine and phosphatidylethanolamine are the most abundant, followed by phosphatidylinositol.
Lipid droplets vary greatly in size, ranging from 20 to 40 nm to 100 um. In adipocytes, lipid bodies tend to be larger and they may compose the majority of the cell, while in other cells they may only be induced under certain conditions and are considerably smaller in size.