The epic of the Tea Horse Road, one of the longest trade routes of the Ancient World, was inspired by this particular tea from the southern part of Yunnan known as Xishuangbanna. Named after the town that was the collecting point for the surrounding tea mountains, Pu’er is made from trees growing in the motherland of tea itself. This is the heart of the Tea Belt, which stretches from Assam to northern Vietnam, no less than the origin of the species. Tea has been grown by hill minorities such as the Bulang and Akha (Aini in Chinese) for at least a thousand years, and it is from here that tea cultivation spread across China—and the world. In the 7th century, the newly powerful Tubo Tibetan Kingdom conquered much of what is now Yunnan, coming into contact with tea. It may also have been introduced when the Tang dynasty Emperor Taixong gave Princess Wencheng’s hand in marriage to the Tibetan King Songtsän Gampo. In either case, Tibetans developed a craving for tea that persists to this day, because it filled a dietary and health gap, relieving the oxidative stress of living at the high altitudes of the Tibetan plateau. The Chinese government turned this into a controlled trade, because it wanted something in return—sturdy Tibetan war horses for the Imperial Army. The six types of tea—green, white, yellow, Oolong, black and Pu’er—are classified by the way they are processed, and Pu’er uniquely depends on what is called post-fermentation. Unlike other teas, it continues to ferment after packing, and its flavour profile improves, as with a fine wine properly stored. Originally, this ageing happened over the months that the cakes of tea were carried on horse back along the Tea Horse Road, protected from the elements only by bamboo-leaf wrapping.