Damon Centola is a Professor Communication, Sociology and Engineering at the University of Pennsylvania, where he is Director of the Network Dynamics Group. He is a leading world expert on social networks and behaviour change. His work has been published in Science, Nature Human Behavior, Proceedings of the National Academy of Sciences, American Journal of Soci- ology, Circulation and Journal of Statistical Physics. He is also a series editor for Princeton University Press, and the author of How Behavior Spreads, a counterintuitive theory for how social networks influence the spread of behavior. His new book, Change: How New Ideas Take Off and Take Hold, is a bold and paradigm-busting new theory about the complex way ideas and behaviors spread, and how to efficiently effect the change you want to see in the world.