Around 6–8% of Earth's land surface is covered in them, and some are considered among the oldest living things on Earth. They can grow almost anywhere, survive in the most extreme conditions and are often the first organisms to colonise fresh rock surfaces after landslides. While some have lost the ability to reproduce sexually, they continue to evolve and form new species.

Lichen really are hardy little guys - but what exactly are they? Well, despite their appearance, they aren’t plants - nor are they closely related to moss or any other plant. They’re composite organisms made of algae or cyanobacteria.

There are approximately 20,000 known species of lichens and they range in colour, sizes and form. An Arctic species called map lichen has been dated at 8,600 years old!