One of the major challenges in biology concerns the integration of data across length and time scales into a consistent framework: how do macroscopic properties and functionalities arise from the molecular regulatory networks and how do they evolve? Morphogenesis provides an excellent model system to study how simple molecular networks robustly control complex pattern forming processes. In my talk, I will focus on lung and kidney branching morphogenesis and discuss how chemical signaling and mechanical constraints shape the developing organs. Using light-sheet microscopy, we can observe epithelial dynamics during branching at cellular resolution, and I will discuss the physical principles of epithelial organization.