This chapter develops an analytical framework for understanding how migrant transnationalism varies across space and changes over time. It is concerned with micro-level transnational practices between migrants and their non-migrant counterparts in countries of origin. The central tenet is that variation in such practices can be broken down into two factors: differences in the prevalence and in the substance of transnational ties. The former concerns the existence of cross-border connections between individuals, primarily in the form of kinship, and the latter concerns the extent to which these connections are conduits for transnational practices. Remittance transactions stand out as a transnational practice that is important in diverse contexts and lends itself to making analytical points about prevalence and substance. Much of the chapter makes use of this example, with empirical illustrations.