Tea Cake: Also known as compressed tea or round tea. In the early Northern Song Dynasty, "Ding Jin, the Fujian transport commissioner, first created Phoenix Cakes," later followed by Dragon Cakes. Dragon and Phoenix Cakes were used as imperial tribute tea until the Ming Dynasty. In the Ming Dynasty, "in the ninth month of the 24th year of the Hongwu reign, the emperor, considering the heavy burden on the people, abolished the production of Dragon Cakes, ordering only tea buds to be offered as tribute." Today, the production technique of tea cakes is primarily preserved in Pu-erh tea, which better enhances its characteristic of becoming more fragrant with age.

Regarding the bitterness of Pu-erh tea: "Unresolved bitterness" refers to the common astringency in tea, where "cannot transform" means the bitterness does not turn sweet and lingers in the mouth. Good tea can transform bitterness into sweetness, with better teas transforming more quickly and the sweetness returning faster. Its "bitterness" is cool and expansive. For example, in ancient tree tea, the bitterness disappears rapidly, immediately giving way to sweetness that lingers pleasantly in the mouth for a long time!