Before a baby's first deliberate smile, caregivers often wonder whether every grin, gaze, and twitch carries meaning. The Social Smile in Babies explains how early facial movements develop into responsive, relationship-building expressions, and how to notice them without turning normal variation into a test. You will learn the difference between reflexive smiles, smiles linked with comfort, and the emerging social smile; how vision, hearing, alertness, feeding, sleep, and familiar voices shape interaction; and why corrected age matters for babies born early. Clear guidance helps you respond warmly through eye contact, talking, imitation, songs, and playful pauses while respecting a baby's cues and limits. The book also addresses missed smiles, changing expressions, cultural expectations, neurodivergence, and when a persistent concern deserves a conversation with a pediatrician or health visitor. Grounded in mainstream developmental knowledge, it offers observation prompts, practical examples, and reassurance without promising certainty or demanding constant cheerfulness. It celebrates the smile as one part of a much richer conversation between baby and caregiver. Part of The Smile and Happiness Library.