This book, for the first time, brings together and updates the ground-breaking work of renowned risk theorist and researcher Ortwin Renn and integrates the major disciplinary concepts of risk in the social, engineering, and natural sciences. The book unfolds through consecutive acts, opening with the context of risk handling and flowing through the core topics of assessment, evaluation, perception, management, and communication, culminating in a look at the transition from risk management to risk governance and a glimpse at a new understanding of risk in (post)modern societies. The focus is on systemic risks, such as genetically modified organisms, that load high on complexity, uncertainty, and ambiguity