This paper considers ethnographic materials devoted to the study of the end of childhood in relation with the social history of medical devices. Forged in the nineteenth century to measure and monitor human groups considered unstable (colonial subjects, retarded, gypsies), these anthropometric devices supported the standardisation of a “good growing” pattern through different stages. Nowadays some traces of such processes appear in the self-measurement of children and adolescents who measure regularly the changes in their body sizes in order to renegotiate their status and capacity to act in consideration of themselves and others.