This undergraduate thesis finds its purpose in presenting general review of tardigrade biology and ecology. Tardigrades (Tardigrada) are protostomic invertebrates of microscopic size varying from 0,1 to 2 mm, what places them in meiofauna. Formerly they were assigned various systematic positions, but today tardigrades are considered members of Ecdysozoa superphylum. There are over thousand described species divided into three classes. Their fairly simple anatomy is similar to that found in arthropods, annelids and onychophorans. Cryptobiosis, i. e. surviving low temperatures, drought and high doses of radiation is the best known remark of tardigrades. Evolution of Tardigrada still remains partialy unclear, but phylogenetic analyses have proven their closer relationship to onychophorans than nematodes. Tardigrades have cosmopolitan distribution which extends from marine and freshwater, to terrestrial biotopes. Although mosses and lichens are the most common and best investigated tardigrade habitats, they were also recovered from glacier ice and hot springs. Ecological role of tardigrades, as well as other meiofauna members is is not negligible, and, in fact, proves complex trophic relationships on a broad range of microhabitats. Tardigradological investigations have been intensified during the last decade. Once again, that is a reminder tardigrades are not obscure, but less-known phylum of the living world, posing a challenge not only for classical zoology, but for fundamental life science research.