Throughout development and adult life, the growth and remodelling of living tissues is determined by a complex interplay between chemical and physical cues. Among such physical cues, mechanical tension is emerging as central regulator of cellular fate and function. To explain tension regulation, current research emphasizes molecular mechanisms at an ever increasing level of detail. How these local mechanisms are integrated to give rise to global patterns of tissue tension is unknown, however. The goal of this project is to provide a multiscale understanding of tension regulation within epithelial cell monolayers. We propose two pairs of competing mechanisms for tension regulation: fluidization vs. reinforcement and cell division vs. apoptosis. These competing mechanisms are inherently multiscale in the sense that they span and couple multiple levels of tissue organization, from the local actomyosin contraction to the multicellular rearrangement. For each of these competing mechanisms we plan to study how local processes and interactions give rise to global tensional patterns. To do this, we propose to develop an integrated experimental setup to map and perturb monolayer tension at different length scales. We expect this project to unveil the repertoire of mechanisms that epithelial tissues use to regulate their tension and dynamics.