Fig. (3) Human osteosarcoma cells isolated and cultured in non-adherent culture/ultra low attachment surface tissue culture plate (100x magnification). A). On day (D)1 all spherical cells were not attached to substrate with tight density within the serum-free and hypoxic medium; B). On D7 The cells formed sarcospheres and reached ~ 80% confluence (P1); C). After sarcospheres transferred back into non-adherent culture plate, spherical cells were not attached to substrate again ; D) and E). Those cells reformed sarcospheres on D14 (P2) on D21 respectively.