The result of Inhelder’s research with adolescents who are confronted with experimental devices that they try to understand and the INRC logic model of Piaget, this book takes up the functionalist perspective present in the trilogy about the baby, benefiting from the achievements of the period of genetic structuralism. It examines how the subjects acquire and use their instruments of knowledge, examining the “methods of discovery and experimental trials characteristic of the adolescent” (p. 2).