**Table 3.**

*Comparison among the methods of slow freezing, vitrification, and ultrarapid vitrification.* 

 CPAs (1–2 M final concentration) to minimize chemical and osmotic toxicity and to maintain a balance between the factors that influence cell damage [23]. Following equilibration, the samples are loaded into straws and cooled at 1–2°C/min to −5 to −7°C and then seeded to initiate extracellular freezing. Thereafter, the samples are cooled slowly at 0.3–1°C/min until they attain the temperature anywhere between −30 and −70°C [24, 25] and finally the samples are plunged into liquid nitrogen for storage. The controlled cooling of samples is achieved with the help of a programmable freezing machine. During controlled cooling, exchange of water molecules takes place between the extracellular and intracellular fluids without adverse osmotic effects [26]. Nevertheless, the extracellular and intracellular water precipitate and form ice crystals during slow cooling [27].
