"Prosthesis" and the "human hand" have been terms used by various philosophers in order to describe the interaction that binds together the human being and the technical artefact -- Martin Heidegger and Jacques Derrida being among the most important of these philosophers. In Bernard Stiegler's philosophy, however, these notions are quite important for another reason: they open up the possibility to rethink the child through the hand, which is, in some respects, the entry point into the human. With the hope of sketching the beginnings of a new philosophy of childhood, I study in this paper Stieglerian prosthesis, showing that it is at its heart an organology; namely a philosophy of the organs (physiological -- as the human hand, and technical -- as the pen). Then, I focus on some more aspects of these processes, underlining the importance of interiorization and exteriorization, but also suggesting an equally important process of figuration and metaphoricity that takes place within consciousness, above, and beneath it. In the last section of the paper, I revisit Stiegler's account of the transitional object in order to sketch a possible opening for forming a philosophy of childhood that takes into account not only memory and the brain, but also figuration and the child's hand.