Eli5: How are embryos frozen and thawed?

Question

I can’t begin to grasp this, I think I get how they are created – but how are they frozen and then thawed to be transplanted into a uterus?
How do they survive?

In: Biology

Answer 1

After being fertilized and grown for several days, the cells are exposed to a protectant fluid which replaces the water inside of them. They are then frozen in liquid nitrogen, and stored at a temperature so low that it essentially halts all of their metabolic processes. They can be kept frozen for years, and the majority of the eggs remain viable after this process.

Source: [Johns Hopkins](https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/freezing-embryos)