Nanoarchaeum equitans is special because it's the smallest known free-living organism and a hyperthermophile, meaning it thrives in extremely hot environments.

Here's a breakdown of its key characteristics:

* Size: It's incredibly small, with a diameter of only 400 nanometers, which is about 40 times smaller than a typical bacteria.

* Symbiosis: It's an obligate symbiont of the archaeon Ignicoccus, meaning it can only survive in association with this other organism. This is because it lacks the genes to perform certain essential functions like amino acid biosynthesis.

* Hyperthermophile: It can only survive in extreme heat, with an optimal growth temperature of 90°C (194°F).

* Unique genome: It has a very small and compact genome, only containing about 490 genes.

* Unique metabolism: It has a unique metabolism that involves the use of hydrogen gas as an energy source.

These features make Nanoarchaeum equitans a fascinating and intriguing organism that provides valuable insights into the evolution and diversity of life on Earth.