Lipid droplets (LDs) are composed of a chemical substance called "lipids". Lipid droplets are storage organelles in the center of lipid and energy homeostasis. They have a unique structure composed of a hydrophobic core of neutral lipids, which is surrounded by a phospholipid monolayer modified by a specific set of proteins. Due to the diversity of lipid droplet functions, their abnormalities are associated with many pathological states.