Named for a town in China's Yunnan province, Pu Ehr teas consist of larger leaves that can be aged for several years. Often, the most highly prized Pu Ehr teas will actually have a light dusting of mold. Pu Ehr leaves are usually compressed into various shapes before being aged. During the aging process, Pu Ehr teas are exposed to microflora and bacteria that ferment the tea, in a way similar to wine or yogurt. The process takes longer though, and the tea's flavor profile can change drastically and increase in depth over many years. Like fine wines, many connoisseurs become collectors of very old and well-aged Pu Ehr. Some of the most highly regarded and expensive teas of this type are well over 30 years old. Pu Ehr teas yield a dark, hearty brew that is low in caffeine. The taste is usually earthy and mellow, lacking much of the astringency of other types of tea. Chinese tradition says that Pu Ehr aids the body with digestion, while new studies indicate that Pu Ehr may help in reducing cholesterol.