This discussion paper aims at presenting the theoretical roots of the transdisciplinary research mode, which is widely used today to address societally relevant research questions. We offer an overview of the literature, the facets that need to be observed and taken into account when research is designed in a transdisciplinary way, and the problems and limitations of this holistic approach. We illustrate how results are generated in transdisciplinary research projects, mainly using the concept of co-creation, which means expanding the expert network to engage practitioners, citizens or other stakeholders in the research process. We provide an overview of the most popular tools and methods. In the remaining part, we present best practice examples for transdisciplinary research to assess common features of success. We collect a number of approaches for stakeholder engagement and policy advice, not neglecting the challenges such an approach entails. Throughout the manuscript, contributions from eminent scholars in the field of transdisciplinary research offer valuable insights on key topics.