Human action is guided by social structure, but there are also many situations in which behavior is improvised, emergent, and outside conventional normative constraints. This book focuses on these types of occasions, which include panics, crowds, social movements, and organized behavior following disasters. Social scientists in the fields of collective behavior, social movements, and disaster research study these topics. E. L. Quarantelli, cofounder and longtime director of the Disaster Research Center (DRC), is one of those scholars; indeed, he has devoted his career to understanding them. Quarantelli's impact on the fields of disaster research and collective behavior is traced in the foreword to this volume.