Growth Factors is a term used to describe a broad range of structurally diverse molecular families and individual proteins best known for their ability to enhance cell proliferation and growth. They have an array of putative functions during development including regulating tissue morphogenesis, angiogenesis, cell differentiation, and neurite outgrowth. They also play important roles in the maintenance of tissue homeostasis and wound healing in the adult. Their activities are mediated via binding to transmembrane receptors that often contain cytoplasmic tyrosine kinase domains. When unregulated, many growth factors and their receptors have been implicated in tumor formation.