Were you aware that this small living organism is in fact two little organisms living symbiotically? Lichens are made up of a tiny alga sandwiched in between layers of fungi. The alga manufactures carbohydrates, which provide food for the whole organism and the fungus absorbs moisture and gasses from the air to help in this process. These organisms, ranging in colour from grey-greens to yellows and reds, can be found in a variety of places where there is enough light and moisture to sustain them. They can withstand long periods of drought, only beginning to grow again when there is moisture in the atmosphere, or rain. They can grow in almost any place in the world as they can survive extremely low temperatures of 196°C below freezing, where they provide an essential source of food for a variety of animals living in these icy conditions, such as antelope and caribou. On the other hand they are also found in the tropics growing best in areas with a regular rainfall pattern or in damp conditions.

The most interesting things about these tiny organisms is that they are a good indicator of pollution as they cannot survive in areas where the air is too polluted, due to the fact that they absorb chemical substances from the atmosphere and the rain that falls on them. They are especially sensitive to sulphur dioxide, a gas given off when fossil fuels are burned.