When I was young, I only heard of two kinds of tea: big bowl tea and Biluochun. Later on, I met tea because I studied traditional Chinese medicine and discovered that tea is also a medicine. For example, in the summary of materia medica, it is recorded that "tea tastes bitter and sweet. It enters the Jueyin meridian of hand, foot, Shaoyin, Taiyin. It can clear the heart and lungs and cleanse the intestines and stomach. It can cure headache by chamomile. It can be used to drink ginger water after drinking. It can be used to introduce the bladder and kidney meridians." However, tea is cold after all. I am naturally weak in the spleen and stomach. I remember once drinking Pu'er tea, half way through it, I went to the bathroom. Later, I seldom drink tea, but an encounter changed my opinion. Not long ago, I went to the Wudaoying Hutong near the Yonghe Temple in Beijing and came to a small shop. The owner of the shop is my good friend and invited me to drink Biluochun. This is a type of green tea. It was time for dinner, how dare I drink green tea on an empty stomach? So he politely declined. But my friend said, try it and make sure it's not cold. She said that the tea originated from an 80 year old tea tree, which was picked from the mountain of Dongting Lake, facing the sun. This is the first batch of pre Ming tea picked by this tree. After manual picking and green killing, and using firewood, it will not be like other green tea. Unable to resist persuasion, I sat down and tasted Biluochun. After drinking a few cups into my stomach, I was surprised to find that my stomach and intestines felt slightly warm and comfortable, without any hint of diarrhea. I let out a few breaths, feeling quite comfortable, and even feeling full. I didn't leave until 8 pm and drank tea on an empty stomach without any discomfort. There was also a slight feeling of fullness and hunger, and warm tea entered my stomach with a slight sweat, making me very comfortable. Later, my friend gave me some of this Biluochun. When I went back to drink it, I felt the same every time. It seems no coincidence. This encounter changed my understanding of tea, especially green tea, and also reminded me of an elderly person who once said that his father was over ninety years old and had been drinking tea for a lifetime, resulting in a long and healthy life. The same goes for the elderly. I initially thought it was due to physical fitness, but now it seems that it's not entirely the case. Recently, after careful consideration, I suddenly realized something. Although tea has a cool nature, its ultimate warmth depends largely on two factors: one is the growing environment, whether it is a cold and humid place, or a warm and sunny place. Just as the grapes in the north are different from those in Xinjiang, the traditional Chinese medicine is achyranthes bidentata, the Cyathula officinalis invigorates blood, and the Huai achyranthes bidentata in Henan nourishes the liver and kidney. Like ginseng, ginseng produced in Northeast China has a warm nature, while American ginseng is cooler, both of which have different origins. The essence of different origins lies in different growth environments, including temperature, sunlight, soil, and planting methods. The second is the processing method, which may be more important. Most tea needs to be blanched, and one step in blanching is to bake it over fire. Traditional Chinese medicine believes that traditional Chinese medicine and raw herbs processed with artillery often have different cold, hot, warm, and cool properties. For example, raw licorice has a cold and cool nature that can clear heat and detoxify, while roasted licorice can strengthen the spleen and replenish qi; Raw Rehmannia glutinosa has a cool nature and promotes blood circulation, while cooked Rehmannia glutinosa steamed by fire has a slightly warm nature and can tonify the kidneys. Most medicinal herbs processed by fire have some warmth, and of course, it depends on the specific method of heating, and even the firewood and oven are not the same. There are many processes involved in the processing of tea, many of which involve fire making, baking, or steaming. This tea making process determines the cold, warm, and cold of tea. I used to think that fermented tea, such as black tea and black tea, was not cold because I didn't understand the fermentation process of tea