Farmers in China’s Yunnan Province have been quietly growing tea for thousands of years. This mountainous region, which borders Vietnam, Laos, and Myanmar, may be the birthplace of Camellia sinensis, the bush that gave rise to all tea. The area’s signature cakes of sun-dried, fermented leaves, known as pu’er, have long been a staple of daily life. To hit the road (specifically, the South Silk Road, which became known as Tea-Horse Road), sellers wrapped dried leaves in bamboo and strapped the discs to their animal. On the journey, traders, horses, and goods were exposed to sunshine, heat, and rain. Fermentation began, perhaps, as nothing more than consequence.

Today, locals press leaves (from Camellia sinensis var. assamica) into dense bricks, then age them for weeks, months, or even years to produce pu’er. The more tightly a cake is compressed, the longer it takes to age. When the tea is deemed ready, drinkers use a knife to chip off bits for brewing. Its flavor and aroma varies greatly with time. Tasters describe younger pu’er as “vegetal and fragrant with gentle bitterness and a tickling sun-dried pungency” and older varieties as dark, elegant, and earthy.

In the 1990s, wealthy outsiders noticed the humble operation. Pu’er, which holds government designation as an exclusively Yunnan-made good, became an object of desire. China’s elite gave the aromatic bricks in festive wrapping as gifts—something to be enjoyed, shared, and felt. Fans often treat it as much like a drug as they do a drink, describing a subtle, incomparable high from drinking the brew and asserting that no two bricks produce a tea that tastes the same. Between the 1980s and 2000s, prices skyrocketed from pennies per kilo to hundreds of dollars for the same product. Like wine, there are even prized vintages of pu’er. In the case of one 64-year-old vintage, a die-hard fan shelled out $150,000 for a mere 500 grams.