Tardigrades are a phylum of organism, near the limit of visibility, some fraction of a millimeter long. They are adapted to every environment on earth, can survive at the bottom of an ocean or the top of a mountain. They can dehydrate and go into suspended animation for a month at a time. They have been found in clouds and in hot springs and in the coldest places we know.
They have been around since the first multi-celled animals, about 500 million years ago, and they are likely to still be around 500 million years from now. In fact, they are so hardy that people who believe life came to earth from elsewhere, hitchhiking on meteors, cite tardigrades as a possible seed organism from space.
Tardigrades have their own phylum, which means that they are not closely related to insects or to worms or spiders or hydras--they're tardigrades.
No eyes and a roto-rooter mouth--not too pretty, but hey--what do you imagine they think of us?