Pu-er,Pu'er, Pu-erh, is a another tea category, Pu-er could well be called Chinas mystery tea. It has been produced in Yunnan from ancient times. Pu-er is a variety of post-fermented tea, post-fermentation is a tea production style in which the teas undergo a microbial fermentation process after they are dried and rolled. Pu-er may be compressed into many shapes or left loose and, unique among teas, it actually improves with age. The best Pu-er comes from the area called the Six Famous Mountains in Xishuanbanna region. Chinese also call the Pu-er category Heicha or Dark tea.