The charm of Chinese medicine can be seen everywhere in our lives. From the simple finger, there are many ways. Commonly known as “health lines”, we are no strangers, in fact, also known as crescent marks. “Crescent” scientific name nail half-moon, one-fifth under the nails, a white curved trace, it is the yin and yang meridian boundary, is the body’s essence of the representative, which is why it is called health lines. What is a normal “crescent moon”? Normal nails, red, curved, smooth and shiny, the root of the nail half-moon grayish-white, the whiter the better. What is the relationship between the crescent moon and age? A healthy person should maintain 8 to 10 crescents on the fingers at the age of 30; at the age of 40, there should be at least 6; and at the age of 60, there should be at least 1 to 2. Usually, maintaining 8 to 10 is ideal. The size and color of the crescent also changes with age. Generally the older you get, the smaller and shorter the crescent will become and the color will go from white to darker. The crescent moon on people’s fingers will be reduced or lost with the occurrence of physical diseases, and once the body recovers, the crescent moon will grow back slowly. It is a misconception that the bigger the crescent mark, the better! The crescent area of a healthy person is roughly 1/5 of the fingernail! If the crescent area is less than 1/5 of the fingernail, it indicates a lack of energy and poor gastrointestinal absorption. If the crescent is smaller than 1/5 of the fingernail, it indicates a lack of energy and poor absorption capacity of the stomach and intestines. If the crescent suddenly becomes dark, shrinks, or disappears, it means that the person is suffering from a consumptive disease, a tumor, or internal bleeding. If the crescent is larger than 1/5, it means that the heart muscle is enlarged, and it is easy to suffer from cardiovascular and cerebrovascular diseases, hypertension, stroke and so on. It can be said that the crescent is a “barometer” of human health.