Excerpt of introduction: It is by now a truism that international migration is a process, not an event. As evidenced by the contributions to this handbook, the cultural, demographic, economic, political, and social causes, content, and consequences of international migration as a process are well documented. However, there remain lacunae and among all the processes embedded within international migration, the complexities of the reciprocal relationship between the sending state and its emigrants has recently begun to receive the detailed attention and critical analysis that it deserves. Following a historical overview, which includes a discussion of the different forms and structures that states have used to maintain or reinforce the relationship with their diasporas and a brief examination of emigration as a human right, we discuss the relationship between sending states’ and economic development with a particular focus on the function and impact of migrant remittances, both economic and social, and of alternative mechanisms of capital flows. Further, we analyze the implications, opportunities, and challenges for the sending state of brain drain, its corollary brain gain, and their change to brain circulation and we assess the reciprocal political relationship between emigrants (exiles and expatriates) and their state of origin. We conclude with some assessment of how states, emigration, and concepts of citizenship are interlinked and we offer some suggestions for future research on the relationship between the state and its emigrants.