The noses of many mammals, such as dogs, ferrets and cows, feature grooves forming a multitude of polygons. A team has analyzed in detail how these patterns form in the embryo using 3D imaging techniques and computer simulations. The researchers discovered that differential growth of the skin tissue layers leads to the formation of domes, which are mechanically supported by the underlying blood vessels. This work describes for the first time this morphogenetic process, which could help explain the formation of other biological structures associated with blood vessels.