This book provides a comprehensive and thorough interpretation of Beck's theory of the (world) risk society, from its original formulation up to his sudden death on New Year's Day 2015. Beck's entire body of work is divided into four interrelated phases, which are successively presented and discussed, namely: the original theory of risk society (from 1986 onwards); the theory of the world risk society (from 1996 onwards); the theory of cosmopolitanism and cosmopolitanization (from 1996 onwards); and the theory of 'metamorphosis', 'emancipatory catastrophism and 'global imagined risk communities' (2013-16). The book thus demonstrates how Beck's concept of the (world) risk society has given us a new language or a special lens that enables us to better understand contemporary society's complexity and its myriad of human-made uncertainties in terms of climate change, terrorist threats, global pandemics, economic crises, and migration crises.