The social question is back. Yet today’s social question is not primarily between labour and capital, as it was in the nineteenth century and throughout much of the twentieth. While class has always been criss-crossed by manifold heterogeneities, not least of all cultural ones around ethnicity, religion, and language, it is these latter heterogeneities that have sharpened in situations of cross-border migration over the past decades. As in the nineteenth century, political conflicts arise, constituting the social question as a public concern. The contemporary social question is located at the interstices of the global South and the global North. It finds its expression in movements of people seeking a better life or fleeing unsustainable social, political, economic, and ecological conditions. It is transnationalized because migrants and their significant others entertain ties across the borders of national states in transnational social spaces; because of the cross-border diffusion of norms; and because there are implications of migration for social inequalities within national states. Casting a wide net in terms of conceptual and empirical scope, this book tackles both the social structure and the politics of social inequalities. It sets a comprehensive agenda for research which also includes the public role of social scientists in dealing with the transnationalized social question.