As the word lichen derives from the greek noun λείχειν leichein, meaning “to lick”,
one can say that lichen is the pioneer species who licks all kinds of surfaces on our planet.
6-8% of planet Earth’s surface is covered by lichens.
Lichen sometimes clings to rocks, always eats from air.

Lichen does not have roots.
Lichen is a being of several organisms coexisting in one body;
a stable symbiotic association between fungus and algae.
A lichen’s fungal part makes up its structural body, while its algae parts executes photosynthesis.
A lichen’s symbiosis or body-sharing is often said to be mutualistic and not parasitic, although the fungi benefits mostly from this relationship. Lichens are fungi that have discovered agriculture. Lichens are algae using fungi as host to see the world.

Lichens are hotels and homes for other beings.

Lichen is a self-contained miniature ecosystem.
An arctic species called “map lichen”  (Rhizocarpon geographicum) has been dated at 8600 years, apparently the world’s oldest living organism.
The European Space Agency has discovered that lichens can survive unprotected in space.