TWG28 brought together researchers in collaborative settings in mathematics teacher education. In many instances the settings involved learning or lesson studies. However, there was much diversity in the studies in terms of types of collaborations and who they involved, research methods and the analytical framing of the studies that informed contributions and discussions. We report here an overview of our work and in doing so highlight this diversity and richness across the corpus of contributions to the TWG. Our discussions were wide-ranging and explored the full complexity of researching teaching and learning that is close to professional practice. Here we give the briefest of insights into the depth and breadth of the contributions that fuelled our work, and which have provided much for participants to consider as they take their research forward.