 Social mobility is the movement in terms of employment, education or income from one level to another. Not being denied that chance because of gender or ethnic group or because they grew up on the wrong side of the railway tracks. Developing countries have been grossly understudied so far. And there are good reasons to believe that the need for social mobility is even greater in developing countries than elsewhere. This book tells us what we know and frames how we should think about research in the future. Our interest in this book is focusing on low and middle income countries. Bringing together for the first time perspectives and insights about social mobility from different disciplines and from different parts of the developing world. A combination of these approaches would actually allow perhaps for the first time a more comprehensive understanding of social mobility. This is why we need to have economists, political scientists, sociologists, anthropologists and historians working together. So far the focus has been on making sure that households cross the poverty line. This is not enough. What happens to those who move above the poverty line? Social mobility studies enable us to get a better handle on what we might do better in order to raise people's standards of living. This book is going to be important both for future research and for future policy about social mobility and inequality reduction. UNU wider has had the history of setting the agenda on critical issues of research and policy. This book follows in the same tradition. Ultimately social mobility is about an equality of opportunity, the most profound inequality one can imagine. Social mobility gets the heart of that and that's why it matters.