Learn how to create and nurture communities of care for diverse children, families, and practitioners through responsive practice. In this text, the social and emotional worlds of babies and toddlers, their peers, and their caregivers come to life in the everyday moments of infant-toddler care and education. The authors show infants and toddlers as active, agentic, and intentional social partners from the start of life, highlighting their unique capacities for social engagement with both adults and peers. Interwoven within each chapter’s narrative are insights culled from extensive observations, teacher interviews, and video analyses. Part I emphasizes play, peer friendships, and humor as essential elements of infant learning, illustrated throughout with anecdotes of praxis in early care and education settings. Building on these aspects of babies’ ways of being in group care, Part II examines the complex roles of infant-toddler professionals and the critical importance of supportive and caring environments. Readers will explore the elements needed for in-depth and specialized professional preparation, including overarching principles of relationship-based practice.