More than 30 years ago, the ground-breaking work by Lester Salamon and Helmut Anheier launched global interest in research into the Third Sector. Yet the world is changing, and the relevance of the Social Origins Theory developed from the Johns Hopkins Comparative Nonprofit Sector Project is now questioned. Third Sector organizations and movements remain vitally relevant and yet, the changing environment and definitions of the field, availability of new data sets, and gaps in the countries and topics studied, all point to the need to take stock and ensure that future Third Sector research is relevant and impactful. This chapter introduces the book, which aims to illustrate, comment and criticize the state of the art and to highlight future possible pathways in which Third Sector research could progress. It seeks an inclusive dialogue that, through encouraging diverse voices, shapes our collective understanding of the sector, its potentialities and hence can ameliorate prior difficulties. This book seeks to spur further research drawing on up-to-date databases and frameworks and to inspire new and seasoned researchers to undertake vital work.