Emigration, Laguerre argues, does not simply drain a nation; it redistributes it. He proposes the cosmonation, a nation whose homeland and its diasporic settlements together form a single crossborder social formation, as a way past both methodological nationalism and loose talk about the nation's disappearance.

Nations are sorted first by shape: monoterritorial ones with a single homeland and a dispersed diaspora, multiterritorial ones assembled through colonisation, annexation or merger. Either can become multisite, and the book follows how such entities are built and held together through migrant associations, expanded consular services, diasporic representation in homeland parliaments, and digital media.

The evidence comes from interviews with French, Italian and Croatian migrants in the United States, with comparative material from Turkish, Greek, Haitian and Armenian informants, alongside content analysis of association and government websites. Crossborder immigrant organisations, operating in several sites at once and sometimes partnered with states, serve as the clearest case.