Multicellular organisms are composed of cells with identical genomes but different properties and functions. They all develop from one cell to form multicellular structures of astounding complexity. I will present how cellular interactions generate emergent tissue scale properties and drive spatio-temporal coordination during development and regeneration. Moreover, I will present the molecular mechanisms underlying intestinal organoid self-organization and the role of cell-to-cell variability in populations of differentiating cells during symmetry breaking.