The interaction of human beings with their environments is rarely direct; behind each one of the direct interactions usually stands a previously mediated interaction. The environment of young children is rather tightly controlled by adults who select, amplify, and interpret different features of this environment for children. As children grow up their understanding of the world becomes more and more mediated by symbolic tools: texts, pictures, diagrams, and formulae. These tools in their turn are acquired via different structured activities: games, formal learning, work apprenticeships, and so on. Greater attention to mediated interactions helps us to understand how a brain becomes a “human mind” in the sense of being shaped by interactions specific to human society in all their various historical and cultural forms.