The purpose of this chapter is to present the hypothesis that cognitive development can be considered as the construction of internal organizations of contents (internal memories) and not as the construction of new structures as Piaget states. The hypothesis consider that Piaget's general coordinations of action are preformed and related to subcortical structures. It is on the basis of these preformed structures, that internal organizations of contents (memories) occur by means of cortical structures (in particular parieto-frontal and occipito-temporal).