One point of clarification about black tea (in parts of China, they call it “red” rea): It’s not fermented. Somehow that term has come into popular usage, even among tea producers. Black tea’s actually oxidized, which means it’s just exposed to the air, and thus turns green leaves to brown. Perhaps the connotation of “rust” that the word “oxidation” implies makes “fermentation” seem more palatable to consumers (particularly 18th century Englishmen used to drinking ale).