The vast majority of world trade flows is between firms. Only recently has research in international trade started to emphasize the importance of the connections between exporters and importers both in aggregate trade flows and in the negative relationship between trade and geographic distance. This chapter documents the role of firm-to-firm connections in trade flows and the formation and duration of these importer-exporter relationships. Using customs data from Colombia for 1995-2014, we are able to identify both the Colombian importing firm and the foreign exporter in every Colombian import and export transaction. We document both the nature of these bilateral trading relationships and their evolution over time.