Modern states have introduced complex legal mechanisms to address the membership or not of an individual to the nation-state. Denis Scuto's doctoral thesis analyzes the construction of Luxembourg nationality, the Civil Code to today, clearing the influences of Belgian legislation, French and German. Far from being limited to only part of Luxembourg, his approach, enriches reflection on the various forms taken by the construction of citizenship in Europe in modern times. Methodogically, questions of nationality are here not reduced to the legislative aspect; they are intimately linked to the practices and discourse relating to migration and migrants. Should European states open them or not access to nationality? How is the perspective of migrants themselves? The social study of hundreds of naturalization records reveals both motivations and hopes of migrants. The thesis tackles a key challenge faced by the country today who, like Luxembourg, experience strong immigration: how to include the right of the most possible people nationality in a political and social project of common future?