This chapter introduces the trend of nexus formation in international politics, which climate-security links are part of. The chapter begins by outlining the patterns of nexus formation in contemporary international governance. Touching on related literature in IR and development studies, it presents the theoretical considerations by Ernst Haas about the formation of issue-linkages in international politics, describes more recent literature on the potential of nexuses as a governance approach and outlines existing critical perspectives toward nexuses. Finally, it considers how the study of nexuses can benefit from empirical studies on the processes of their formation, and from the consideration of the role of knowledge resources – in particular in the case of environmental issues, which depend significantly on scientific knowledge.