It is commonly observed that most societies in the world have now become multicultural—assuming they were not already so. Ethnoracial diversity—whether caused by migration, state formation processes that unfolded in pluri-ethnic conditions, populations descended from non-indigenous slaves, the presence of colonized or now decolonized populations—has reached what is probably an unprecedented level since the late nineteenth century. And it has many types of effects: demographic, political, social, cultural, economic, and others. The aim of this extensive project is to retrace the demographic, political and/or social dynamics that produced this population diversity and to study the changes it has brought about in these now multicultural societies, all of whose structural aspects have been affected, and the social practices of groups in a situation of “superdiversity”, i.e., living in societies, cities or neighbourhoods where the cohabiting “groups” form minorities whose numbers are in fact comparable to those of the majority group. The practices in question encompass social interactions as well as matrimonial, religious, health-related, political, residential, cultural and linguistic practices. The research projects will also cover educational or employment strategies and trajectories. The field locations are French; project studies include international comparisons.