FGF2, or Fibroblast Growth Factor 2, is a growth factor involved in signaling pathways important for cell growth, proliferation, differentiation, angiogenesis, and migration. It is also known as basic fibroblast growth factor, bFGF, FGF-b, BFGF, FGFB, HBGF-2, heparin-binding growth factor 2, and prostatropin. FGF2 is a 288-aa residue secreted protein and is a member of the FGF family, which is noted for its affinity for heparin and the FGF receptors. It is expressed in granulosa and cumulus cells, and in certain cancerous tissues. Four to five isoforms have been identified. FGF2 is found to be crucial in keeping human embryonic stem cells undifferentiated, and is used as a culture medium. An immunoassay such as a FGF2 ELISA kit will be a useful tool to identify the presence or expression of this growth factor.