This article can help teachers and directors become eloquent and effective advocates of play-based early learning environments. It defines play and play policy and discusses distinct research areas that support play policy and practice for physical, cognitive, social, and emotional development within diverse early childhood settings. Also presented are three anecdotal examples of current challenges to play-based curriculum. In this article, the author discusses the definitions of play that emerge from three perspectives: (1) the exploratory and open-ended nature of play; (2) the intrinsic, evolutionary, and synergistic nature of play; and (3) the developmental aspects of play. Among other things, she discusses three research foci, namely: (1) active play and health-related indicators; (2) brain research--the critical link between play and optimal cognitive and physical development; and (3) the link between play, early literacy, and social competence.