As was the case in previous editions of this handbook, this chapter is not about cognitive development per se, but about how cognitive development relates to and can be infl uenced by early childhood educators. As before, the content is therefore selective: in spite of the importance of cognition within developmental psychology, I do not survey “all” of the research here (even if it were possible!). Instead I select and frame material according to its relevance to the work of early childhood educators. Since their work usually takes place in classrooms, homes, and other locations with strongly social features, the chapter also has a markedly social emphasis. As a result, some topics with strong research programs, such as the neuropsychology of cognition, receive less emphasis than might be expected. Others, such as information processing theory, are discussed only for their relevance to how early childhood educators might use the research to infl uence children’s cognition. The converse of this practical idea-that educators might use children’s cognition to regulate their social experiences-of course is important as well. It is acknowledged from time to time in this chapter, but is more appropriately discussed elsewhere in this volume (Sokol, Muller, Carpendale, Young, & Iarocci, 2010).