Across childhood and adolescence, youth develop an increasing focus on belongingness within the peer group. At the core of this need to belong lies a motivation to optimize approval and acceptance from peers (which we view as sensitivity to social incentive or reward), as well as a motivation to minimize disapproval and rejection from peers (which we view as sensitivity to social threat or punishment). Integrating several historical and contemporary theoretical traditions, we conceptualize these motivations in terms of social approach and avoidance needs and goals. In this article, we discuss our conceptual and empirical journey that began with mapping the content and structure of social motivation and progressed through exploring how motivational orientations influence children's socioemotional adjustment, how predispositions toward social approach and avoidance develop, and, most recently, how these motivations may be represented in the brain. We end with recommendations for future research aimed at continued unraveling of the complex and nuanced implications of children's sensitivity to both rewarding and punitive social cues.