Neurospheres at days 1, 3, and 5 showing differing sizes in different combination of growth factors. Group A (EGF + bFGF); Group B (EGF + bFGF + IGF-1); Group C (EGF + bFGF + LIF); Group D (EGF + bFGF + BDNF) and Group E (no growth factors). Cells in Group E attached to the flask starting to differentiate (arrows). Neurospheres with irregular shape formed in Group E on day 5 of culture. Images were viewed with 100× magnification under an inverted microscope.