Against the background of the serious threat Western democratic societies are facing from both populist parties and social movements, this work attends to serious lacunae in the debate on populism in the social sciences, particularly in sociology. First, the chapters included contribute to clarifying conceptual uncertainties of what populism actually means; second, they analyse the ways populism develops and turns into a strong political force; third, they thoroughly discuss the most critical aspects of recent populist debates as security, social exclusion, migration, religion, gender, and law.