FGF2 and teratoma: This test, which is considered an in vitro surrogate for the teratoma formation test, helps to verify the potential of hiPSCs to be differentiated into virtually any cell type of the body and is performed by triggering a random differentiation of pluripotent cells by subtraction of both the adhesion stimuli and basic fibroblast growth factor (bFGF), the key factor that maintains cells in an undifferentiated state.