This paper proposes a framework to better understand the diffusion of radical innovations. Following Abernathy and Clark (1985), we consider that the high degree of uncertainty and the prevailing ambiguity which actors face in such situations require new frames for action at the individual and collective levels. While the exploration phase and the nurturing of radical innovation is well studied up until the development of niches and protected spaces, the move to the exploitation phase, and thus the transition to the markets is less understood. We argue that this weakness lies in under-estimating the critical importance of market structuration. Market structuration requires a specific work from actors by developing ‘market infrastructures’ during the transition. Under uncertainty, actors work on want-to-be market infrastructures: their work is thus only a tentative governance of market work. We highlight the fact that the governance for nurturing radical innovation is different from this of markets. We illustrate our proposition by analyzing the on-going case of nanotechnologies.