Growth factors are molecules that play a role in the regulation of cell growth, proliferation, and differentiation. They are involved in the healing and repair of skin tissue. They work by signalling to cells to divide and grow, which can help to promote the formation of new skin cells and blood vessels. Some skin care products contain growth factors to promote wound healing and improve the appearance of the skin. There are 4 types of growth facors – skin cells (epidermal growth factor, EGF) nerve cells (nerve growth factor, NGF) connective tissue or mesenchymal cells (fibroblast growth factor, FGF) thrombus-forming cells that line blood vessels (platelet- derived growth factor, PDGF). Growth factors can be sourcced from epidermal cells, human foreskin, placental cells, colostrum, recombinant bacteria, yeast, and plants. They can also be produced biosynthetically.