The document outlines the TRANSIT project led by DRIFT at Erasmus University Rotterdam, which aims to develop a theory of transformative social innovation (TSI) that promotes systemic societal change. It addresses key research questions related to the conditions under which social innovations lead to such transformations and examines the roles of actors and game-changers in the process. Furthermore, the project includes empirical studies of transnational networks and emphasizes the need for a better understanding of the relationship between theory and practice in social innovation.