The first uncoupling protein discovered, UCP1, was discovered in the brown adipose tissues of hibernators and small rodents, which provide non-shivering heat to these animals.[1] These brown adipose tissues are essential to maintaining the body temperature of small rodents, and studies with (UCP1)-knockout mice show that these tissues do not function correctly without functioning uncoupling proteins.[3] In fact, these studies revealed that cold-acclimation is not possible for these knockout mice, indicating that UCP1 is an essential driver of heat production in these brown adipose tissues.[7][8]