The hypothalamus is a largely heterogeneous structure that has been difficult to functionally dissect, but the ability of optogenetics to precisely target specific cell-types and projections has allowed for the characterization of circuits mediating feeding and aggression. POMC and AGRP neurons in the ARC play opposing roles on feeding through AGRP inhibition of ARC-POMC and PVH-OT neurons to evoke feeding. In addition, activating neurons in the VMHvl acutely and reversibly induces aggression. Abbreviations: AGRP, agouti-related protein; ARC, arcuate nucleus; OT, oxytocin; POMC, pro-opiomelanocortin; PVH, paraventricular hypothalamus; VMHvl, ventrolateral subdivision of the ventromedial hypothalamus.