Modern societies face several structural problems such as transport congestion and greenhouse gas emissions due to the widespread use of fossil fuels. To address these important societal problems and achieve sustainability in the broad sense, major transformations are required, but this poses an enormous challenge given the complexity of the processes involved. Such transformations are called 'transitions' or 'system innovations' and involve changes in a variety of elements, including technology, regulation, user practices and markets, cultural meaning and infrastructure. This book considers two main questions: how do system innovations or transitions come about and how can they be influenced by different actors, in particular by governments. The authors identify the theories which can be used to conceptualise the dynamics of system innovations and discuss the weaknesses in these theories. They also look at the lessons which can be learned from historical examples of transitions, and highlight the instruments and policy tools which can be used to stimulate future system innovations towards sustainability. The expert contributors address these questions using insights from a variety of different disciplines including innovation studies, evolutionary economics, the sociology of technology, environmental analysis and governance studies. The book concludes with an extensive summary of the results and practical suggestions for future research. This important new volume offers an interdisciplinary assessment of how and why system innovations occur. It will engage and inform academics and researchers interested in transitions towards sustainability, and will also be highly relevant for policymakers concerned with environmental issues, structural change and radical innovation.