How do embryos survive the freezing process?

They first dehydrate the embryo to remove the water, that route when it is frozen, no ice crystals form, which is what would exterminate it.
they go underneath dorment condition------------cell wall breaks and cell lose all cytoplasim contents except DNA just DNA survive without any metabolic process
The cell division process get halted as the cell change state from liquid to solid. The cell are kept bacteria free and so survive the process until neccessary.