When cells are cryopreserved

the morphology of cryoprotectant at crystallization and recrystallization would influence the survival rate of cells.The cryo-microscope system was used to observe the morphology of crystal and sizes of two cryoprotectants during cooling and rewarming at different speeds.It is found that crystals during cooling are smaller and less at higher speed than at lower speed

and the former is favorable for preservation of cells.When the vitrified cryoprotetant is rewarmed

crystals during recrystallization are smaller and less at higher speed than at lower speed

and the former with narrow danger zone is favorable for the survival of oocytes.Besides

high concentration of cryoprotectant is more favorable for the survivalrate of oocytes than lower concentration.