Drawing on an ethnographic survey undertaken in a school in a workingclass neighbourhood, this article analyses the process of appropriation of Skyblogs by young teenagers, in a context of mass diffusion of blogs in that age-group. Blogs are seen as instruments in targeted activities and as the outcome of a constructive activity by users. The author shows that for these students the meaning of blogs evolves along with the development of their sociability and the construction of their identities. The youngest ones use blogs above all as instruments for incorporating the norms and values of juvenile culture, while the older ones create blogs as tools for expressing themselves within the group.