Despite the global success of development in reducing poverty, hundreds of millions of people still live in abject poverty and danger, in shanty towns and favelas, or in rural communities and tribal lands. They live in poorly governed or conflict zones that have been shelled to pieces, and they suffer from climate change, famine, crime, and corruption. “Putting People First”, Michael Cernea’s mantra first published in his seminal book of the same name, rings even more true now than ever. The phrase originated at the World Bank, more than 40 years back, when that institution was at its most significant as the world’s largest and leading development finance institution. “Putting People First” became a movement. This book documents how concepts and strategies from applied social science can be used to improve the quality of international development and thereby people’s welfare and life prospects. The book recapitulates and presents voices from the time, decades ago, when social specialists first joined an international development insti tution, the World Bank. They were guided by Michael Cernea, the World Bank’s first social scientist. This book presents the story of how change in a large develop ment agency became possible. But the essays contained in this book are of more than historical interest. Social development continues to matter if we are to make progress in solving some of the world’s major new social challenges—from internal and international migrations to ethnic, cultural, and religious divides, to collaboration on managing the global commons—our shared climate, water, oceans, and biodiversity.