Résumé : recent advances in robotics leads us to consider, on the one hand, the notion of a kernel, a set of stable algorithms that drive developmental dynamics and, on the other hand, variable body envelopes that change over time. this division reverses the classic notion of a fixed body on which different software can be applied to consider a fixed software that can be applied to different kinds of embodiment. thus, it becomes possible to study how a particular embodiment shapes developmental trajectories in specific ways. it also leads us to a novel view of the development skills, from sensorimotor dexterity to abstract thought, based on the notion of a fluid body in continuous redefinition.