This structured review examined (academic) publications on flipped or inverted classrooms based on all Scopus database (n = 530) references available until mid-June 2016. The flipped or inverted classroom approach has gained widespread attention during the latest decade and is based on the idea of improving student learning by prepared self-studies via technology-based resources ('flips') followed by high-quality, in-class teaching and learning activities. However, only a few attempts have been made to review the knowledge of the field of interest more systematically. This article seeks to address this problem and investigates what constitutes the research on flipped classrooms and, in particular, to examine the knowledge contributions with the field so far in relation to the wider research topic of educational technology. This review found that the current state of flipped classrooms as a field of interest is growing fast, with a slight conference preference and a focus on higher education and STEM (science, technology, engineering and math) area contributions, with the US as the predominant geographical context. It is concluded that studies on flipped classrooms are dominated by studies in higher education sector and are relatively local in character. The research tends not to interact beyond the two clusters of general education/educational technology and subject-specific areas. This implies that knowledge contributions related to the flipped classroom approach are relatively siloed and fragmented and have yet to stabilise. Academically and socially, the research is quite scattered, and only local evidence and experiences are available. The knowledge contributions within this field of interest seem to be anecdotal rather than systematically researched. To a large extent, the research lacks anchoring in, for example, learning theory or instructional design known from educational technology traditions and which would have helped much of the flipped classroom research to examine aspects of the flipped classroom approach more fully.