Tardigrades are pretty cool. I never really looked into them until I stumbled on this video. If you prefer to learn about them in written form, you can just read the Wikipedia page. But the video here is worth the watch and not too long.
Tardigrades are among the most resilient animals known, with individual species able to survive extreme conditions – such as exposure to extreme temperatures, extreme pressures (both high and low), air deprivation, radiation, dehydration, and starvation – that would quickly kill most other known forms of life.