Tardigrades

Tardigrades, known colloquially as water bears or moss piglets, are a phylum of water-dwelling eight-legged segmented micro-animals

They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them kleiner Wasserbär  i.e little water bears. 

Scanning electron microscope (SEM) image of Milnesium tardigradum in active state. source: wikipedia/Schokraie E, Warnken U et al

In 1777, the Italian biologist Lazzaro Spallanzani named them Tardigrada, which means "slow steppers”.

Waterbear

SEM image of a tardigrade clearly showing 4 pairs of legs. image: Bob Goldstein and Vicky Madden, UNC Chapel Hill/wikipedia

All around the world

They have been found everywhere, from mountaintops to the deep sea and mud volcanoes, and from tropical rainforests to the Antarctic.

Super resilient creatures

 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. Tardigrades have survived exposure to outer space.

How big are they and what do they look like?

Tardigrades are usually about 0.5 mm (0.02 in) long when fully grown.[1] They are short and plump, with four pairs of legs, each ending in claws (usually four to eight) or suction disks.

Where do they usually live and what  do they eat?

 Tardigrades are prevalent in mosses and lichens and feed on plant cells, algae, and small invertebrates. 

source adapted from: Wikipedia contributors. (2020, October 22). Tardigrade. In Wikipedia, The Free Encyclopedia. Retrieved 09:35, October 24, 2020, from https://en.wikipedia.org/w/index.php?title=Tardigrade&oldid=984898494