This paper has two aims. The first is to show the usefulness and intuitiveness of frame theory in reconstructing scientific classification systems. The second is to employ such reconstructions in order to make headway in the scientific realism debate and, more specifically, in the question concerning scientific theory change. Two case studies are utilised with the second aim in mind. The first concerns the transition from the phlogiston theory to the oxygen theory of combustion, while the second concerns the transition from the caloric theory to the kinetic theory of heat. Frame-theoretic reconstructions of these theories reveal substantial structural continuities across theory change. This outcome supports a structural realist view of science, according to which successful scientific theories reveal only structural features of the unobservable world.