Chaga (Inonotus obliquus) is a parasitic fungus that grows primarily on birch trees in cold climates — Siberia, Northern Canada, Alaska, Scandinavia, and Korea. It appears as a large, dark, charcoal-like mass (called a conk) on the outside of trees and has a rich, cork-like interior. Chaga has been used in Siberian folk medicine for centuries, brewed as a tea to boost immunity and vitality. It is one of the richest known sources of antioxidants in the natural world, with an ORAC (antioxidant) score dramatically higher than most fruits and vegetables.