{HEAD ~ The invention} involves immersing a mammalian tissue or cultured tissue equivalent in a cryoprotectant solution, agitating the cryoprotectant solution and the immersed tissue to achieve effective penetration of the cryoprotectant solution into the tissue, and then freezing the tissue at {TAIL ~ a very slow freezing rate} at 0.3° C. or less/min 
{ HEAD ~ The invention } involves immersing a mammalian tissue or cultured tissue equivalent in a cryoprotectant solution , agitating the cryoprotectant solution and the immersed tissue to achieve effective penetration of the cryoprotectant solution into the tissue , and then freezing the tissue at { TAIL ~ a very slow freezing rate } at 0.3 ° C. or less / min
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