Neurosphere formation was seen with phase-contrast microscopy of GBM CD133-positive tumor cell culture. Single tumor cells were sorted for CD133 expression by magnetic bead cell sorting to collect CD133-positive cells. Single CD133-positive cells were then cultured. Neurospheres were seen when single CD133-positive tumor cells were cultured in EGF- and bFGF-containing, serum-free medium. The left panel is before culture of CD133+ cells (t: 0 day), and the right panel after six weeks (t: 42 days). (Left panel, scale bar = 50 μm; right panel, scale bar = 100 μm).