The transforming growth factor-beta (TGF-beta) family comprising a large group of extracellular growth factors controls the development of the organism. TGF-beta family members consists of a large number of structurally related polypeptide growth factors, each capable of regulating a fascinating array of cellular processes including cell proliferation, differentiation, motility, adhesion, and death. TGF-beta and related factors play a prominent role in the development, homeostasis and repair of virtually all tissues in organisms.