Obesity and opioid overuse are global epidemics and major causes of death. Public awareness of the addictive properties of food and opioids has been growing progressively throughout the last decade. Both addiction and overeating are disorders in which individuals learn rewarding associations between stimuli and outcomes. Excessive intake of calorie-dense palatable food despite negative consequences mimics compulsive drug use. Therefore, we are studying the roles of genetically-identified cell types and their projections in driving feeding behaviors and the ways in which these behaviors become compulsive. In addition, we are examining how neurons in distinct hypothalamic circuits encode pain. Thus, we use optogenetics and chemogenetics to manipulate neuronal circuits in awake, behaving mice. Moreover, we use a combination of electrophysiology, two- and single-photon fluorescence endomicroscopy, and behavioral assays to elucidate the neuronal basis of such survival behaviors (i.e. feeding and pain) and to determine how theses circuits drive the rewarding and addictive nature of food intake and drugs of abuse.