Pu-Erh

Pu-erh is the only tea that improves with age, and the only one that actually undergoes a fermentation. The tea starts as either a green or partially-oxidized tea that is dried and then piled up beneath a damp cloth and "fermented" for days or weeks and then dried again. This type of pu-erh is called "shou" or "mature/ripe" pu-erh. (Another type is "sheng" or "unripe," which is stored for a long time until the flavor ripens slowly in the humid climate of southwest China.)

The Chinese have long considered pu-erh tea medicinal and good for quenching thirst, digesting oily foods, reducing cholesterol, detoxification (as a diuretic), aiding in weight loss, among many other things.