Soluble growth factors are potent regulators of normal and pathological processes. Mechanical factors are emerging as similarly important, but there has been no obvious mechanism linking the different factors. A recent report now demonstrates that cell-generated mechanical tension results in release of active transforming growth factor–β from stiff extracellular matrix, providing a mechanism for differentiation and maintenance of myofibroblasts in processes like fibrosis. More broadly, the work suggests that matrix stiffness could regulate the equilibrium between storage and release of a host of matrix-bound growth factors.