Toughest animal on the planet:The water bear that can survive being frozen or boiled

It's often said cockroaches could withstand a nuclear explosion.But another creature, dubbed 'nature's greatest survivor,' is even more invincible, and you've probably never even heard of it.

Tardigrades, also known as water bears, are some of the most fascinating animals in world because they can live happily in the most extreme conditions.

The creatures can survive tremendous heat and cold, radiation and vacuum

The animals, pictured, can live happily in the most extreme conditions

This Tardigrade or water bear comes from Roan Mountain, Tennessee

While not the most attractive creatures, the small, segmented animals come in many forms - there are more than 900 species of them - and they're found everywhere in the world, from the highest mountains to the deepest oceans.

Boil the 1mm creatures, freeze them, dry them, expose them to radiation and they're so resilient they'll still be alive 200 years later.

Water bears can hack temperatures as low as -457 degrees, heat as high as 357 degrees, and 5,700 grays of radiation, when 10-20 grays would kill humans and most other animals.

The animals can also live for a decade without water and even survive in space.

Tardigrades feed on plant and animal cells and are found throughout the world, from the tropics to the cold polar waters

While not the most attractive creatures, the small, segmented animals come in many forms

The water bears are often found in moss

There are more than 900 species of Tardigrade or Water Bear, pictured

They're found everywhere in the world, from the highest mountains to the deepest oceans.

Boil the 1mm creatures, freeze them, dry them, expose them to radiation and they're so resilient they'll still be alive 200 years later

This tiny invertebrate lives in aquatic and semi-aquatic habitats such as lichen and damp moss

Water bears can hack temperatures as low as -457 degrees and heat as high as 357 degrees

Molting Water Bear or Tardigrade with an egg mass

Water Bear's can surivive 5,700 grays of radiation, when 10-20 grays would kill humans and most other animals

This Tardigrade or Water Bear is infested by fungi

The animals can also live for a decade without water and even survive in space