Motivated by the challenges of the green transition in cities and considering the above limitations of orthodox - nineteenth century guided -economics and the conceptual richness of complexity and their main instruments the proposed research question is: How changes in the behavior of socio-economic actors due to the green transition and environmental policies could imply transformations in the economic complexity and development of cities, resetting the levels of organization of urban systems (micro, meso and macro)?

To answer this question, a bottom-up and top-down model could be developed, characterized by being highly decentralized, composed of a multitude of heterogeneous agents - i.e. households, firms and cities - focused on the green transition, integrating a multi-level approach that allows to simulate several scenarios under which this transition is produced, resulting from dynamically changing micro-behaviors.