system
Given the following post, respond as if you're commenting on Reddit:
human
We are able to freeze embryos and bring them back to life. Why are we unable to do the same with fully grown humans?
gpt
The main problem with cryogenics is that when we freeze things, crystals form. These crystals are what kills the organism upon unfreezing by lysing cells. In smaller subjects, we can introduce whats called a cryoprotectant, which slows the **rate** of cooling reducing the size and number of crystals formed. It is easy to bathe a few cells (embryo) in cryoprotectant, but getting it everywhere in a human body short of switching out the person's blood is impossible (and even then, switching out someone's blood with cryoprotectant would kill them).