How do students learn to explain? We take this exemplary research question for presenting two antagonist traditions in German mathematics education research and their synthesis in an ongoing video study. These two traditions are (1) the German Didaktik approach that can be characterized by its epistemologically sensitive analyses and specifications of mathematical contents, and (2) the interactionist approach. By presenting the theoretical framework and some empirical insights, the article shows that learning to explain can be conceptualized as increasingly participating in navigating practices through different epistemic fields.