To start with the first: the biographical approach shows us how the early, trial and error methods of 'being an expert' steadfastly developed into more crystallised views on their roles. The experts based their methods on the early-career understandings of the relationship between science, politics and the public domain. This article opens up the biographical-narrative 'black box' of these experts, and the enactment of that biography in practice (Goffman 1959; Deuten and Rip 2000; Brockmeier and Carbaugh 2001) . Learning experiences, personal or communal reflections on specific events, the continuous process of re-narrating and reframing past experiences, all added up to an individual conviction on 'how to perform as a credible expert'. In Coutinho's case, we might say that his self-perception as an expert has not changed dramatically, but solidified in a repertoire of communicating the facts. Goudsmit, on the other hand, following a redefinition of his expertise, radically changed the way in which perceived his role in policy and in public debate. Then we have Osterhaus, who still finds himself in a continuous balancing act between a credible scientist, a policy entrepreneur, a public communicator and an industry advisor. The biographical-narrative approach has elucidated how each of them have accommodated themselves in the boundary zone between science, policy and public debate, and thus juxtaposes with a more macro-sociological understanding of expertise, such as Nowotny's 'narrative of expertise' (Nowotny 2000) .