Pu-erh tea

„The fermented dark tea, Hei Cha (黑茶), is one of the six classes of tea in China, and pu-erh is classified as a dark tea (defined as fermented), something which is resented by some who argue for a separate category for pu-erh tea.“

„Fermentation is a tea production style in which the tea leaves undergo microbial fermentation and oxidation after they are dried and rolled. This process is a Chinese specialty and produces tea known as Hei Cha (黑茶), commonly translated to dark, or black tea (this type of tea is completely different from what in West is known as "black tea", which in China is called "red tea"). “