 Transforming growth factor beta, TGF-beta proteins play a key role in the development of fibrosis by stimulating excessive production of collagen and other structural components of the extracellular matrix, ECM. This leads to scarring and thickening of the affected tissues, which can cause serious damage to organs and tissues. Additionally, TGF-beta ligands have a natural affinity for the ECM, resulting in a concentrated pool of profibrotic factors at the site of injury. As such, TGF-beta ligands are upregulated in many human-fibrotic conditions and are therefore attractive targets for fibrosis therapies. This article was authored by Kelly L. Walton, Catherine E. Johnson and Craig A. Harrison.