Reactive oxygen species (ROS) are thought of as toxic byproducts that cause injury to our tissues and drive pathologies associated with aging.   However, recent evidence is emerging showing that under certain conditions ROS can be important signals in healthy tissue.  In this study, the Spiegelman Lab examined these ROS signals in brown adipose tissue, which contain cells that have the specialized ability to burn stored fats as heat and combat obesity and diabetes.  They found that increases in ROS levels in brown adipose supported thermogenesis in living mouse models.  Moreover, they demonstrated that ROS signals involved the direct modification by ROS of key functional targets including the critical thermogenic protein uncoupling protein 1 (UCP1).  These findings suggest that modification of ROS processes and this newfound signaling site on UCP1 provide new and unexpected ways of manipulating thermogenesis to combat obesity and diabetes.