Have you ever heard of lichen?   It doesn’t get the same attention that bigger, more exciting living things get -- like elephants, or sharks, or giant redwood trees.    But it’s one of the coolest things that you’re likely to find on your next walk in the woods -- or even in your own back yard!   Lichen is a tiny living thing, or organism, that grows outdoors, attaching itself, most of the time, to rocks, trees and soil.    This small but colorful organism really likes moist areas, which is why you can find it where water runs down rocks, on the bark of damp trees, and on the wet ground.   But here’s a surprise---lichen is actually two different organisms that live together to help each other out.    It’s actually both a fungus and an algae.    You may have seen fungus on the bottom of your old bread at the bottom of the bag.    Gross, I know, sorry. But that fuzzy green mold is a kind of fungus, and mushrooms are part of a fungus, too.   As for algae, you might’ve seen that on the inside of your fish tank, or wherever there’s still water, like a pond.   In lichen, fungus and algae work together in a relationship called symbiosis. A symbiotic relationship is where two organisms help each other survive, with each of them getting something out of the relationship.    Both the fungus and the algae bring special skills to this party. The fungus is bigger and has a stronger body than algae, so it gives the lichen its shape.    But the algae has another role. The algae brings home the bacon...by which, I mean, it makes food.    Not bacon.   Like many other plants, algae can make food from sunlight. It uses a process called photosynthesis to capture energy from the sun to make sugars that it uses for energy.   Since the fungus can’t do this on its own, it pairs up with the algae to help get a steady supply of food.    And while algae can survive on its own, wherever there’s water and light, pairing up with the fungus allows it to grow in all kinds of different landscapes, like moist, sandy places, wooded forests and rocks!   Once you learn how to spot it, it can be pretty easy to find in all sorts of places.   It can be blue, green or red. Or yellow! Or even orange! The color of lichen depends on what type of fungus and algae are working together.   But there are three main types to look for. The first kind is leafy like lettuce. But don’t eat it!   The second kind can grow to look like little teacups, or the wispy strands of an old man’s beard. You may have seen this type swaying in the wind on tree branches.    And the last type is called “crust lichen.” It’s colorful and flat - you can find them on rocks. And it makes the rocks look like they have spots!   Whatever the shape and color, lichen is very diverse and it's also very delicate. It grows extremely slowly, so if you happen to see some while you’re on a hike, try not to step on it!   While it may be small, lichen is an important part of nature, because it provides a home for little critters like spiders and small insects.   And here’s a fun fact! - Lichen usually grows where the air is fresh and clean, which is why you can find them out in natural areas, like in forests and around lakes, but not necessarily near highways or in the city.    So if you’re out on a walk with your friends or family, and you see a little sprig of lichen on a tree or a rock, take a deep breath of fresh air! Ahhh.   Thanks for watching Sci Show Kids. See you next time.