Migrants moving from Mexico to the United States represent the world's largest migration corridor, and the two countries have a long, complicated history with respect to immigration. Previously a country of emigration, Mexico increasingly has been experiencing new roles: as a country of transmigration and increasingly of settlement. The research here examines Mexico's relationship with its vast diaspora in the United States; the economic, insecurity, and other factors that have led to sizeable emigration; and the country's evolving policymaking with respect to migration.