Oocyte vitrification achieves significantly higher survival rates than older slow-cooling methods because it prevents ice crystal formation entirely. The mature human egg is one of the largest cells in the body and holds a correspondingly large volume of water. At slow-cooling rates, that water forms ice crystals that physically rupture cell membranes. Vitrification cools at rates up to 20,000 degrees Celsius per minute, so fast that intracellular water transitions directly to an amorphous glass-like solid without crystals forming. Combined with cryoprotectant pre-treatment, this gives survival rates consistently above 80-90% in well-run labs, compared to below 50% with slow cooling.