ABSTRACT The National Synchrotron Light Laboratory (LNLS) is one of the ten institutes linked to the National Council for Scientific and Technological Development (CNPq) and one of the most important investments made in the last two decades by the Brazilian federal government in civil Science and Technology (S&T). The issue I address involves the understanding of how the Synchrotron Project materializes. Such objective implies revisiting the long negotiation process, which lasts through two political regimes and five different governments; and which faced resistance even from scientists and researchers My hypothesis is that the institutionalization of the Synchrotron Project becomes viable thanks to a process that goes from the permeability of the LNLS negotiation process to the imposed transformations by the transition to the democratic regime.