Together with colleagues, I have been using Abstraction in Context as theoretical framework and the associated nested epistemic actions model as methodology for investigating learners’ construction of mathematical knowledge, for about 25 years. In this essay, I show how the features of both, the theoretical framework and the methodology, have been designed for researching construction of mathematical knowledge in a way that takes into account its nature and epistemology; as a consequence, they are suitable for investigating construction of mathematical knowledge in a wide range of mathematical topics and for a wide range of age groups.