We are often told that our world is a world of transnational communities and diasporas. Western states confronted with massive emigration have long been trying to keep in touch, and control, the ones who left, and nurtured networks of information and identities. Having long identified migrants as immigrants, we do learn a lot through these pages, looking at them as emigrants. Transporting concepts like diaspora or transnationalism into the past also lead us to wonder what was exactly new about such things as transnationalism and the multiplication of diasporas. Is it the world we live in, or the tools we use to describe it, or a bit of both? Dealing with different people, different times - from 1820 to 1990 - and different places, the five historians gathered here challenge some of the assumptions of contemporary discourses. They use parts of a theoretical framework designed to identify and name what is new and unprecedented in our world to shed light on previous migrant experiences and it actually works.