An artwork on display in the Yaan Museum shows how dark tea was packed in bamboo holders. [Photo by Zhang Ji/For chinadaily.com.cn]

Most of us think Pu’er when thinking of dark tea, but a visit to Yaan in Southwest China's Sichuan province will surely put a surprise on their faces.

Pu’er is actually a small sub-division of China's dark tea, a category of tea that requires a secondary fermentation process, also called a post-production process. Dark tea is commonly known to have the function of aiding digestion and revitalizing energy, and it has been a daily drink of the Tibetans for more than a thousand years.

There is a saying that "Tibetans can live without food for three days, but cannot go without tea for a day." In the Tibetan plateau where fresh fruit and vegetable are scare, meat, butter and barley are the staple food. Drinking fat-dissolving drink tea is not only a traditional custom but also a physical need.

Dark tea is the essential ingredient of Tibetan butter tea, the indispensable beverage of everyday life for the Tibetans. However, dark tea was not originally produced in Tibet, as its weather and geographical condition are not suitable for growing tea plants.