Lichen
Lichen are actually made up of 2 microorganisms (either a bacteria or an algae and a fungi) living together in harmony!
Lichen can be found growing on plants, trees, soil and even concrete and stone! They can appear in lots of different shapes, sizes and colours because there are lots of types of lichen. The different shapes even have their own names! Crusty hard lichen growing tightly against a surface is called ‘crustose’. Ones that are more flakey often looking more like little leaves are called ‘foliose’. You can even get some that grow like tubes sticking up away from the surface which are called ‘fruticose’!
The growth you see is actually the result of two different microorganisms living together in a symbiotic relationship. This is when two or more living things work together, each providing something the other needs, to allow them both to survive better than they would alone. In the case of lichen this symbiosis involves a fungus (like the individual cells that make up a mushroom) living with either a bacteria or an algae (essentially a microscopic plant). The bacteria or algae provide food for the fungus by using the sun's energy, whilst the fungus makes the relatively tough structure itself to keep them safe.