Spirulina is a blue-green algae, and is believed to be one of the oldest life forms on Earth.

First used by the Aztecs as an endurance-booster, spirulina is considered a superfood — an all-in-one source of nutrients including protein levels comparable to eggs. 

Spirulina has a bitter taste, so people often mix it with yogurts, juices, and smoothies to improve its flavor. Spirulina is commonly available as a supplement at health food stores.