A newborn’s smile can make an ordinary moment feel astonishing—but what does it mean? Why Do Newborns Smile? offers a clear, compassionate guide to the earliest expressions of infancy, from brief sleep smiles and reflexive movements to the social smiles that gradually emerge through warm, responsive interaction. Vivian Cross Harlow explains how developing facial muscles, nervous-system states, feeding, sleep, discomfort, temperament, and early relationships shape what parents see. You will learn what is typical in the first weeks, how to use corrected age when a baby arrives early, and how to notice patterns without turning every expression into a test. Practical observation prompts help you distinguish a smile from a grimace, recognize when your baby may need a break, and share concerns appropriately with a pediatrician or health visitor. Respectful of cultural difference, neurodivergence, parental anxiety, and the full range of infant emotions, this book replaces guesswork with understanding and connection. Part of The Smile and Happiness Library.