This article explores the "wow-effect" as a phenomenon in science teacher education. Through ethnographic fieldwork at a teachers' college in Denmark, the author encounters a phenomenon enacted in a particular way of teaching that "wows" the students. The students are in the process of becoming natural science/technology and biology teachers. This article explores and theorizes the wow-effect by examining tension fields within the phenomenon between boredom and engagement, new and old technologies, and being active and sedentary. By situating this phenomenon in a discussion of theory and practice in teacher education, the author discusses how teaching according to the wow-effect is both engaging for the students as well as problematic in relation to learning certain theoretical aspects of natural science/technology and biology.