Traditional developmental psychology has historically legitimized home-based and maternal care as primary foundations for infants and toddlers’ socioemotional development and wellbeing. Notwithstanding the impact of such disciplinary roots on Early Childhood Education and Care (ECEC), this field has claimed for alternative approaches in dealing with infants’ socioemotional wellbeing, as these pedagogical institutions inherently implicate an expanded network of relations and orientation toward collectiveness. Hence, this chapter addresses the socioemotional development of infants across their transition from home to ECEC according to manifestations of their emotional wellbeing observed either in that collective context and/or in more peer-oriented situations. The analysis is underpinned by a cultural-historical perspective, and it was accomplished through a microgenetic analysis of video recordings encompassing the first 2 months of attendance of two infants (two Brazilian ECECs). We identified manifestation of emotional wellbeing according to the criteria of engagement, openness to interact, relaxation, and sometimes positive affect in collective situations. Departing from this category, we selected and analyzed episodes from both infants. The contrasting developmental trajectories among the two children contextualize and shed light on the complexity of socioemotional dynamics and pedagogical approaches to transitions. The work of supporting emotional wellbeing in a new collective context is discussed.