The course will deal with the role of trees and forest in urban and peri-urban environments, their crucial importance to front the challenge of the current time: ecological crisis, inequalities, functioning of plant communities in the artificial context. Benefits and ecosystem services provided by trees and forest will be analyzed and innovative tracks of their use will be explored, in terms of Green Infrastructures and Nature Based Solutions. Guidelines for the management of trees and forest will also be discussed. the perspective of the dynamic evolution of this crucial component will be presented in its relationships with the circular bioeconomy approach that demands to change the paradigm: nature host cities and not viceversa. The new vision of Biocities for the future will be presented throughout lectures, seminar, laboratories and field activities.