Tardigrade

The tardigrade (phylum Tardigrada), often referred to as a "water bear" or "moss piglet," is a microscopic, eight-legged animal renowned as one of the most resilient life forms on Earth. Measuring typically between 0.3 and 0.5 millimeters, these segmented invertebrates inhabit a vast range of environments, from the deep sea and mountain peaks to tropical rainforests and the Antarctic. They are most commonly found in damp moss and lichen.

Their fame stems from an extraordinary ability to survive extreme conditions that would be instantly lethal to almost all other organisms. This survival is facilitated by a dormant state called cryptobiosis, most notably the form known as tun formation. When faced with desiccation, the tardigrade retracts its legs, loses almost all its body water, and enters a state of suspended animation. In this "tun" state, its metabolism drops to near-undetectable levels.

Remarkably, tardigrades in this cryptobiotic state can withstand temperatures from just above absolute zero to well over 150°C, pressures six times greater than those in the deepest ocean trenches, the vacuum and radiation of outer space, and decades without water. Their resilience is attributed to unique protective proteins, such as tardigrade-specific intrinsically disordered proteins (TDPs), which are thought to vitrify and protect cellular structures when water is absent, and efficient DNA repair mechanisms.

Despite their near-indestructible reputation, tardigrades are not extremophiles in the active sense; they do not thrive in these harsh settings but rather endure them by shutting down their biology until conditions improve. Once rehydrated, they can return to active life within hours. This combination of minute size, charming appearance under a microscope, and phenomenal durability has made the tardigrade a subject of intense scientific study, particularly in astrobiology and materials science, and a celebrated icon of nature's tenacity.

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(britannica)
Tardigrades are invertebrates belonging to the phylum Tardigrada. They are related to arthropods (e.g., crustaceans and insects) and nematodes (i.e., roundworms). Also known as water bears, tardigrades are known for their appearance and their ability to survive in extreme environments. Tardigrades can survive extreme conditions by going into a “tun” state, in which their body dries out and their metabolism drops to as little as 0.01 percent of its normal rate. When conditions return to normal, the tardigrade revives itself. A tardigrade can stay in a tun state for decades.
Research shows that tardigrades can be killed by exposure to hot water for an extended period of time. One study showed that one hour of exposure to water at 82.7 °C (180.9 °F) can kill a tardigrade in its “tun” state, where it goes into suspended animation and becomes hard to destroy.
Tardigrades can be found in moist habitats, such as damp moss or underwater sediment. Tardigrades exist all over the world because of their ability to withstand extreme conditions.