This book investigates the role of social groups in mobilizing resources for protests in repressive contexts. In particular, it examines the impact of organizations and informal groups on individual engagement in the protests developed in 2010-2011 in Tunisia, Egypt, and Syria. Empirical analysis draws on a wave of events and protests that took place between 2010 and 2021. It explores how, in repressive contexts, spontaneous groups and more established and formal organizations continuously switch from one form to another, transforming themselves faster than they would do in democratic contexts.