This book analyzes the informal practices of contemporary cities through a close dialogue between different research perspectives, with the shared goal of giving voice to informality and evaluating its benefits and potential in a multidimensional key of social factors. Recently, the human sciences have seen the emergence of this new term "informality," at first sight in conflict with their function of giving order and form to social phenomena. A term with which, in this book, the authors, having as reference the Italian and European experience, specifically identify those unsatisfied social demands and those collective actions "from below" that aim at the recovery of urban space and the renewal of its organization, often not following the trajectories of legality and institutions. By means of a close dialogue between different areas of social research, this book attempts to establish the different declinations and applications of the term, evaluating the causes and effects, benefits, and potential of the phenomena attributable to it, within a multidimensional analysis that calls into question the regeneration and collective use of spaces, political-institutional confrontation and conflict, legal innovation, and social-economic benefits.