Empirical research shows that adults' role in play with infant-toddlers is to provide children with play materials, observe from a distance, and control the surrounding dangers. An international trend to increase children's cognitive skills at a very early age has established a need to better understand toddler's conceptual learning and how this is supported by the joint play between toddlers and educators. This paper draws upon a cultural-historical perspective, and discusses the concept of play and pedagogical practices of a Conceptual PlayWorld approach to investigate how educators and toddlers generate a Conceptual PlayWorld that supports their conceptual learning and development. We argue that conceptual learning of children at a very young age should be promoted in our institutional practices as it might benefit future scientific learning at school. The educators' affective engagement is the key to developing a powerful collective play environment to strengthen children's conceptual thinking.