This study investigates the molecular mechanisms underlying ligand recognition, subtype selectivity, and activation of neuropeptide FF receptor 1 (NPFFR1)-a Gi/o-coupled receptor that responds to endogenous RF-amide peptides (RFRP-3 from pro-NPFFB, NPFF from pro-NPFFA) and regulates physiological processes like opioid function, pain, and energy homeostasis.