Teacher training for teaching nature of (NOS) is central to didactics of to achieve scientific and technological literacy. The aim of this paper is to describe appropriation processes developed to implement curricular teaching learning Sequence (SEA) on a feature of NOS the observation on science in college students, who are trained as teachers, by an explicit and reflective methodology. The results show that explicit teaching processes are effective and intentionally help to improve students' understanding of role of observation in