Thermogenin (called uncoupling protein by its discoverers and now known as uncoupling protein 1, or UCP1)[5] is an uncoupling protein found in the mitochondria of brown adipose tissue (BAT). It is used to generate heat by non-shivering thermogenesis, and makes a quantitatively important contribution to countering heat loss in neonates which would otherwise occur due to their high surface area-volume ratio.