This book is the first of a work in two parts addressing the relations between the transnational society and the state. It is dedicated to the analysis and conceptualisation of transnational societies. This work moves beyond the mere depiction of transborder socialities by shedding light on the fundamental structures underpinning them. It investigates the mechanics of their formation and evolution, their demise or transformation into diasporas. It theorises transmigrants as plural humans embedded and socialised in multiple settings, and whose activities are sustained and framed by three key social institutions: transnational families, businesses and associations. It sheds light on the construction of an intersubjective moral framework regulating the relations between migrants and non-migrants. Finally, it examines the space-time continuum of transnational societies.