Chaga is a fungus, a parasitic carpophore that looks like the charred remains of burned wood on the side of a birch tree (sometimes growing on Elm and Alder, but Birch is its favorite). It is not the fruiting body of the fungus, but a sclerotia or mass of mycelium. The parasite enters the tree through a 'wound' in the bark of a mature tree. It then grows under the bark until it erupts in a deeply cracked, black charcoal like extension. It usually takes another 5-7 years for it to fully mature, at which point it falls to the forest floor, most times killing the host tree in the process. Chaga has been a part of folk medicine in Russia, Poland, China and numerous Baltic countries for many centuries. It was documented by Chinese herbalist Shen Nong in his herbal texts as early as the first century B.C.E.