system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can human eggs be frozen? Wouldn't they die like every other human cell?
gpt
It is perfectly possible to freeze human cells without damaging them. The trick is speed and the conditions in which they are stored. Freezing an individual cell or small number of cells can be done very quickly. This flash freezing process prevents cell death and changes the size of any ice crystals that form. 

It's harder to do this to an entire organism because of the mass and thermal conductivity of the body. It's just harder to pull all that heat out quickly the larger something gets. You also run into problems of thawing where it doesn't thaw everywhere at the same time, so some parts could become thawed while others remain frozen which would lead to cell death from lack of a heart beat, liquid blood, breathing, etc. You don't run into those problems with individual cells like sperm or eggs. 

It's interesting that a similar process is used in the production of frozen foods. The Birdseye company that created some of the first frozen vegetables for consumers, was founded by a gentleman named Clarence Birdseye who had some experience with indigenous peoples who froze part of their food supply every winter to preserve it. He happened to notice that carefully choosing when the food was frozen had a large impact on it's taste and texture when thawed and that the colder it was and the faster it froze, the less damaged the food became. So food preserved early in the winter tended to be mushy and bland and food preserved later in winter when it got colder tended to be better preserved. The reason for this is the formation of ice crystals and the colder it is when freezing, the smaller the crystals become. Slow freezing produces larger crystals which destroy cells. Whether it was broccoli or fish, the speed of freezing and the temperature it was frozen at, affected the quality of the food when thawed.