Dark Tea 黑茶 hēi chá

Pu'er is the outlier. Every other tea type is defined by enzymatic oxidation — the browning reaction driven by enzymes within the leaf, the same process that turns a cut apple brown. Pu'er is defined by microbial fermentation: bacteria, fungi, and other microorganisms acting on the leaf over time. It's a fundamentally different chemical process, which is why Pu'er sits in its own category — hei cha (dark tea). Raw Pu'er (sheng, 生) starts as a compressed cake and transforms slowly over years through natural microbial activity; it can age for decades and is traded with vintage values. Ripe Pu'er (shou, 熟), developed in the 1970s, uses a controlled wet-piling fermentation that achieves in months what aging achieves over years.