White adipose is the typical fat cell called an adipocyte. The adipocytes contain lipid droplets that fill the middle of the cell and are anchored by collagen fibers. Brown fat cells are smaller in size and quantity, and derive their color from the high concentration of mitochondria for energy production and vascularization of the tissue. The lipid in brown fat is burned to provide high levels of energy as heat in animals who hibernate and infants who may need additional thermal protection.