Children's understanding of cognition increases greatly between early childhood and adolescence. This increase provides a developmental bridge between young children's understanding of mental states to adolescents' and adults' epistemological reflection. The author presents a framework for describing developmental changes in children's understanding of cognitive activities. He distinguishes 4 aspects of children's understanding of cognition: (a) knowledge of mental states, (b) knowledge of occurrence of particular activities, (c) knowledge of organization of cognitive activities, and (d) epistemological thought. He discusses phenomenological awareness of cognitive activities and social experience as influences on children's concepts of cognition.