Tardigrades are the most resilient organism on planet earth. They can survive the hottest and the coldest temperatures, so they are found almost in every part on earth. They can even tolerate a great level of radiation. When they were first discovered, they were called water bears. These creatures follow a process called anhydrobiosis meaning life without water. Tardigrades go through tun state in which they pull their head and eight legs inside their body and roll up into a ball. They stay in tun state until the water is found. Tardigrades can even survive in outer space but they originate from planet earth. There are 1100 species of Tardigrades and many yet to be discovered. Depending on the species, their size range is 0.1mm-1.5mm. Tardigrades mostly eat fluids or plant cells. They even eat other tardigrades. It turns out that tardigrades occasionally, swallow bits of their own mouths, it would hardly be the weirdest thing about them.
Some species of Tardigrades have eyes that aren’t eyes but a single photoreceptor cell. They survive temperatures as low as -272 degree Celsius and high as 150 degree Celsius, extreme radiations and extreme pressure as high as 6000 atmosphere. They have a life span of more than 100 years. To survive extreme situations, their metabolism lowers to 0.01%.
There is a huge misconception about Tardigrades that they are immortal but they are very delicate and can be hurt and killed easily. They get eaten by other single-celled organisms.
But Tardigrades are not extremophiles, they just when stuck in extreme conditions can survive.