Subject and Problem: Scholars and policy-makers widely share the conviction that science education needs to prepare students for making decisions on societal issues that relate to science (EU-Commision, 2004; Millar & Osborne, 1998). In the past decades there has been an increasing focus on supplementing science teaching with a focus on socioscientific issues – i.e. issues that are about what to do, not just what is true (Nielsen, 2011) – e.g. about whether to allow human gene therapy. In such contexts, teachers cannot just guide the learning of and assess the performance of their students in terms of whether they use science evidence or whether the claimed evidence is in fact true (Nielsen, 2013). Consequently, teaching socioscientific issues necessarily puts a demand on teachers to draw on knowledge stemming from other domains, e.g. the humanities (Simonneaux, 2011). This ought to call for pre-service teacher educators to focus on the pedagogical challenges of teaching socio-scientific issues (Forbes & Davis, 2008), but so far few countries have systematically made socio-scientific issues teaching a part of pre-service teacher education (PreSEES consortium, 2013a). ! We implemented a three-step teaching module in which Danish pre-service upper secondary school teachers were taught about the unique pedagogical nature of socio-scientific issues and subsequently designed their own teaching units. This creative aspect of the module was scaffolded by iterative steps of microteaching to peers and teaching to upper secondary school students. The research question clarified by the present study was the following: To what extent does a short indoctrination to, and application of, socio-scientific issues influence pre-service teachers' teaching practice concerning the facilitation and formative assessment of students' socio-scientific argumentation? In other words, we sought to investigate how the pre-service teachers' facilitation and formative assessment of the learners' socioscientific argumentation occurred in both the microteaching session were the pre-service teachers tried out their teaching as well as in the implementation of their teaching in a real upper-secondary school class.