Ulrich Beck is one of the world's most cited social scientists, and among the greatest sociologists of the past forty years. His most important and lasting achievement was to place the concept of risk at the centre of the social sciences. Stimulated by the impact of new challenges and environmental catastrophes, such as climate change and nuclear disasters, Beck developed the influential idea of 'risk society', which emphasized the changing dynamics and distribution of risks in an era characterized by increasing reflexivity and new types of problem which partially defy the old logic of class stratification. In his later writings he developed the idea of risk society further by taking account of other kinds of risks, including financial risks and political risks such as international terrorism, and by examining the impact of globalization. He was Professor of Sociology at the University of Munich and the LSE. Polity published most of his work, including his last book, The Metamorphosis of the World.