Brown adipose tissue contributes to energy balance in humans by generating heat via the mitochondrial uncoupling of lipid oxidation. Currently it is believed that brown adipose has two origins: Myf5-negative progenitor (its source is same as that of white adipocyte) and Myf5-positive progenitor (its source is same as myocyte). Due to the different origins of brown adipocytes, they may be formed via multiple pathways which include the main pathway (by which Myf5-positive progenitors differentiate into brown adipocytes that distribute in classical locations) and alternative pathway (by which Myf5-negative progenitors differentiate into brown adipocytes that distribute in white adipose tissue).