This timely book introduces readers to the central question of borders in the twenty-first century. After familiarizing readers with border thinking and making from antiquity to the present, Gabriel Popescu turns a critical eye on current concepts, processes, and contexts. Assessing the latest theoretical approaches to border studies, the author deftly incorporates a range of disciplinary perspectives, including geography, international relations, sociology, history, security studies, and anthropology. He explores recent world events, discussing how current issues such as migration, terrorism, global warming, pandemics, the international human rights regime, outsourcing, the economic crisis, supranational integration, regionalization, and digital technology relate to borders and influence our lives. Written with a clear eye and voice, this book makes a complex subject accessible to a wide readership.