Lichen is not a single life-form, but a symbiosis - a partnership between a fungus and a green alga or cyanobacterium growing together.
There are more than 20,000 known species of lichen. Through history, humans have found many uses for lichen as dye, food, animal fodder and medicines. Today, lichen’s main use is as a vital ingredient in the perfume industry. However, medical research shows that some lichen species contain substances with antibiotic properties, while others could potentially treat viruses and tumours.