Blue Green Algae is today considered a type of cyanobacteria rather than a traditional alga. It is known under many different names, including blue-green algae, blue-green cyanobacteria, and blue algae. Just like algae and plants, it derives energy from the sun through photosynthesis, but it is considered a member of the domain Bacteria and not a plant.

You can encounter blue green algae in a wide range of different habitats all over the planet. Some species are very specialized and can for instance only be found in the fur of sloths in the South-American rainforest. Others live inside other organism, e.g. inside sponges and lichens. The blue green algae are important for the host, since the host gets a share of the energy produced by the blue green algae.

Unlike certain types of green algae, the blue green alga cell is not equipped with flagella to move around with. Some types of blue green algae can however move around by gliding over surfaces or create gas vesicles. Many species reach new places by forming motile filaments. Blue green algae living in colonies can appear as hollow ball, sheets or filaments. In order to survive harsh times, some colonies can produce though and durable spores known as akinetes.