In recent years we have witnessed massive demonstrations of denial, refusal, and rejection exploding in one country after another. The squares of the world have become organizational focal points for rebellion and repression. What does such collective negation mean, and what comes afterward? This issue explores the forms of a reinvigorated, experimental communism: councils, assemblies, communes, squares, occupys, horizontalism, recovered factories, and cooperative farms and community gardens. Practitioners of this new model of "communism as communizing" attempt to change fundamental social relations from the bottom up.By combining insider knowledge with sophisticated theoretical scrutiny, the contributors to this issue approach eruptions of rebellion from a variety of historical, economic, and methodological perspectives. Writing not only about but also within such forces of progressive resistance around the world, they investigate the complex, hopeful, and contradictory process of creating new social, economic, and political structures through negation.