The fibroblast growth factors are a family of cell signaling proteins that are involved in a wide variety of processes, most notably as crucial elements for normal development. Any irregularities in their function lead to a range of developmental defects. These growth factors generally act as systemic or locally circulating, extracellular signaling molecules that activate cell surface receptors, but a defining property of FGFs is that they bind to heparin and heparan sulfate thus some of them are found to be sequestered in the extracellular matrix of tissues that contain heparan sulfate proteoglycans and they are released locally upon injury or tissue remodeling.