Koji, scientifically known as Aspergillus Oryzae, is a filamentous mold, part of the kingdom Fungi. Just like mushrooms, it begins its life as a spore. These spores produce tiny filaments called hyphae, which forms a tight network of mycelium as it matures. Towards the peak of maturity, instead of maturing into a fruiting body like a mushroom, koji matures into a microbial mat comprised of tasty mold. Koji is traditionally grown on rice, barley and soybeans but can be grown on almost all substrates that contain protein and or starch.