Fibroblasts, the most common mammalian connective tissue cells, form fibrous supporting structures consisting of collagen and other extracellular matrix (ECM) molecules. The flat, elongated cells vary in shape from stellate (young) to fusiform and spindle shaped, with cytoplasmic processes present in connective tissue. With their ability to liberate growth factors, lay down fibroelastic matrices, and proliferate at sites of inflammation, fibroblasts play critical roles in wound healing, tissue repair, and remodeling. As immature cells, fibroblasts can differentiate into other connective tissue cells, such as chondroblasts and osteoblasts. Human Dermal Fibroblasts (HDF, from Cell Applications) can also be converted into induced pluripotent stem cells (iPSC), a Nobel-prize awarded technology.