Post-harvest treatment is also essential to distinguish teas: use of whole leaves or crushed leaves, withering, drying, oxidation, fermentation, etc.

With all these distinctions and categorisations, it should be remembered that a universal categorisation exists and allows the majority of teas to be grouped under five classification categories:

• Green teas. Non-oxidised teas. The leaves, after wilting, are heated to a high temperature in order to neutralise the enzymes responsible for the oxidation.
• Black teas. Oxidised teas. They are called red teas in China because of the colour of the infusion, whereas Westerners retain the colour of the leaves. After withering and rolling (rolling breaks up the cells, releasing the enzymes that will allow fermentation), the leaves are left to rest in a hot, humid room for a few hours for oxidation, then dried at high temperature to stop fermentation.
• White teas. Like green teas, they are minimally processed and undergo only slight oxidation, but not rolling or roasting. These are generally high quality teas from very selective plucking.
• Oolong. Oolong or Wulong tea is a type of tea with incomplete oxidation, halfway between green tea, which is not oxidised, and black tea, which is completely oxidised.
  The word Oolong means black dragon and has its origins in a Chinese legend where a planter saw a black dragon emerge from a tea plant whose leaves revealed the woody chestnut and hazelnut notes of Oolong. This tea is also referred to by the colour of its infusion: blue tea. It originated in the Fujian region of mainland China and in Taiwan.
• Pu'Erh. Pu-erh is a post-fermented tea named after the town of Pu'er in the Chinese province of Yunnan. This town was for a long time an important trading centre on the ancient Tea and Horse Road from Yunnan to Tibet. The tea produced in the region was compressed so that it could be more easily transported by caravan to Tibet. Pu'ehr improves with age and, like wine, its value increases with age.