This chapter reviews the newest developments in the understanding of the cognitive development of children. We emphasize the contributions of John Flavell and other cognitive psychologists. Taking as its foundation the work of Jean Piaget, Flavell and his colleagues started understanding “metacognition”, i.e. what children know about “their minds’ and other people’s minds. Multiple studies examined what children know about how other people solve problems, what happens in their minds and what they are thinking. These researchers also studied children’s strategies to memorize and “metamemory”, i.e. how children develop strategies to remember things and how they apply this knowledge to solve novel problems. Theory of mind is a central concept in metacognition and metamemory, understanding how others think and approach problems. Further studies involved social cognition and how children ascertain the intentionality of others. All of these are important in the development of teaching strategies. Furthermore, empirical studies of “inner dialogue” in children allow a glimpse of strategies children use to process everyday experiences and make decisions about concrete and interpersonal problems.