Yellow tea is the rarest of the six major tea colors and is produced only in China, where its traditional processing can be traced back for hundreds of years. Yellow teas are seldom exported and are mainly grown, harvested, and processed in Sichuan, Hunan, and Anhui Provinces. Unlike green teas, which are quickly dried after firing and rolling, yellow teas are piled to achieve partial oxidation after firing. This technique removes the fresh, brisk flavors common to green teas, and develops the golden infusion color and smooth, rich flavors of yellow teas. Chemically, this pile oxidation process involves the conversion of simple tea polyphenols into a group of complex tea polyphenols known as "theaflavins," which yield a yellow pigment in the leaf and create its clear, golden-hued infusion.