Controversy studies have been an important part of the sociology of science since the late 1970s when Merton's more institutional approach to the field began to be displaced by the sociology of scientific knowledge (SSK). Inspired by Fleck, the new sociologists of science were determined to show empirically that knowledge-making was a social process involving struggles between old and new ideas. Controversy studies focused on moments. Two broad streams of research emerged under this heading. The first investigated conflicts over the interpretation of particular observations of natural and social phenomena, giving rise to the methodological concept of symmetry in SSK: that sociologists should use the same explanatory tools to explain why some facts are accepted as true and others as false. The second focused more on wholesale shifts between what Kuhn termed scientific paradigms. Here research encompassed the makers and users of knowledge along with the interpretive flexibility of the observations themselves. This research looked at the formation of thought collectives and forms of expertise associated with the definition and control of new knowledge objects.