Chlorella is a single-celled, green freshwater algae. There are over 30 different species, but two types — Chlorella vulgaris and Chlorella pyrenoidosa — are most commonly used in research.
Because chlorella has a hard cell wall that humans cannot digest, you must take it as a supplement to reap its benefits. It’s available in capsule, tablet, powder and extract form. In addition to being used as a nutritional supplement, chlorella is also used as a biodiesel fuel.