What is more complex than an urban system where human beings, buildings, activities, infrastructures and services all interact in a nonlinear way? Since more than half of the world population lives in urban areas, it is crucial to study this with the appropriate tools.

With absolute competence and fluency, C. S. Bertuglia and F. Vaio delve into the urban phenomenon with the only approach able to decode it: complexity, which has given up all partial views because of their unproductiveness. If a complex system is defined as a whole that acts and evolves according to a logic non reducible to the sum of its parts, the definition perfectly adapts to urban areas, big entities constantly unbalanced that organize themselves and proceed thanks also to an internal antagonistic concept. The goal of the science of complexity is to see clearly through the tangle, seemingly inextricable, of the people who live, work and commute, of physical structures and imposing nontangible networks of goods and transports. C. S. Bertuglia and F. Vaio follow a path from the preindustrial city, entrenched in the territory, to the industrial one, where urbanism is elevated to a form of life, to the megacity of the postindustrial era, where the physical space is replaced by a reticular process that connects production and consumer centres. Between globalization, gentrification and expulsion, today’s dynamics respond to an appropriative and expansive model, where complexity is set against a view from below, mindful of common assets.

Cristoforo Sergio Bertuglia has thought urban planning at the Politecnico di Torino and has been president of the Italian Association of Regional Science and vice president of the Italian Association of Operational Research.

Franco Vaio has thought Math at the Politecnico di Torino. He has been involved in highenergy physics and industrial researches in the field of speech synthesis and recognition. For more than twenty years C. S. Bertuglia and F. Vaio have worked together on the elaboration of mathematical models in the context of regional science. With Bollati Boringhieri they published Non linearità, caos, complessità. Le dinamiche dei sistemi naturali e sociali (2003, n. ed. 2007; Non linearity, chaos and complexity, Oxford University Press, 2005) and Complessità e modelli. Un nuovo quadro interpretativo per la modellizzazione nelle scienze della natura e della società (2011).