Many people who are just starting to get familiar with the study of facial features often feel lost when trying to observe others' appearances, as if they were in a fog, feeling completely overwhelmed and unable to distinguish directions. In fact, to understand and study the study of facial features, as well as other traditional Chinese cultures, it is necessary to find a simple and practical entry point, which is to start from Yin and Yang. Because traditional Chinese culture has one common principle, and every thing is inseparable from the concepts of Yin and Yang. For example, Traditional Chinese Medicine talks about the balance of Yin and Yang in the human body; Feng Shui distinguishes between Yin and Yang sites; and painting and calligraphy emphasize the changes between void and reality. Therefore, in general, if one grasps the overall principle of Yin and Yang, many problems can be easily solved.

Therefore, the so-called study of facial features, in plain terms, is to use the theory of Yin and Yang from traditional Chinese culture to observe a person's appearance and physical form, and interpret and analyze their thoughts. For instance, ancient books on facial features mention that "southerners are observed by their foreheads, while northerners are observed by their jaws." This is because, according to the theory of Yin and Yang, the south belongs to fire, which is Yang, while the north belongs to water, which is Yin. Thus, diviners believe that when observing the face of someone living in the south, the focus should be on the forehead, whereas for someone living in the north, the focus should shift accordingly to the jawline.

For example, the theory of Yin and Yang states that the upper part is Yang and the lower part is Yin, the head is Yang and the feet are Yin, men are Yang and women are Yin. Therefore, when reading a man's face, the focus should be on the head, and when reading a woman's face, the focus should be on the feet. Since men are Yang, and Yang radiates outward, men generally tend to observe the world mainly through their eyes. Women, being Yin, and Yin absorbs inward, so women prefer to learn about life mainly through their ears. Therefore, when observing a man's face, one must not forget to carefully examine his eyes, and when observing a woman's face, one must not overlook her ears.

In Yin and Yang, protrusions represent Yang, and depressions represent Yin. Therefore, by examining whether the Baihui point (the top of the head) is protruding or not, one can know whether the person's internal Yang energy is sufficient. By checking whether the Yongquan point (the arch of the foot) is flat or sunken, one can determine whether the person's internal Yin energy is deficient. On the face, the nose is the most prominent part, standing high, so even the nose of a woman is called "the husband's star" in classical books on facial features. The term "husband's star" refers to the star of a man. Therefore, from the perspective of facial features, a person whose nose is clearly sunken and low is considered an unfavorable facial feature, regardless of gender, indicating a lack of support for a man's career development and happiness, and lacking the ability to assist a husband.

According to the standards of human aesthetics, there are several very important focal points when appreciating a woman's beauty: the cleavage, the hip groove, the navel, and the ankle. However, these are also the best observation points for women in the study of facial features. Because the deep and recessed grooves and eye-like structures are symbols of Yin in nature and the human body. The more Yin energy there is in heaven and earth, the deeper and more mysterious the distance of the grooves and eyes becomes. Therefore, a woman who has normal innate development and proper postnatal nutrition and care, and is physically and mentally healthy, will naturally display some distinct physical characteristics different from men. These grooves and eye-like structures distributed on the surface of the body are the most important manifestations of a woman's form. While most people see only a woman's beauty and sexiness, a facial feature scholar can use these grooves and eye-like structures to predict a woman's future life and journey.