system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why cant we freeze humans and unfreeze them 100 years later? Is the freezing the problem or the unfreezing? or both?
gpt
Humans are mostly made of water. 

Water forms crystals when frozen. 

Those crystals are sharp and cut apart the human on a cellular level. 

All the ways we know to stop water from forming crystals when cooled to freezing temperatures are toxic to humans in the concentrations needed.