It’s called Spirulina.

Spirulina is a natural food source that has 58 times the iron of raw spinach and 28 times that of raw beef liver. This food was a significant part of the Aztec and Mayan diets. It contains more beta-carotene than any other whole food, and is very high in chlorophyll. It is 65% proteins and amino acids. This amazing food is the richest source of natural antioxidants of any whole food, containing every natural known antioxidant. NASA plans to grow this food on the space station, as it is one of the most efficient, oxygen generating foods in existence. It contains all the B vitamins, and is an extraordinary
“transport” of other vitamins, allowing your body to actually benefit from all the other foods and vitamins you take. It is a blue-green algae that produces all its nutrients by harvesting sunlight. Since Spirulina has become so popular the world over, it is now cultivated in carefully controlled organic ponds, eliminating any possible toxicity. Spirulina.com is a great website with simple yet complete information on each step of the process of growing, harvesting, drying, and preserving the algae.

This comes in powder form or pill form. The powder form is a little hard to swallow and it tastes nasty. I add it to apple juice. The pill form is much easier to take.