Observe the interior and exterior of the Interior body refers to the inside of the human body or to the internal environment of the body, while outside refers to the surface of the body or to the natural environment of which human beings are dependent.A human being is an organic whole and is closely related to the natural world. When a sick person, safe disease is closely related to a functional disorder of the Zang-Fu organs, Qi and blood, as well as the meridians and collaterals.The pathological changes in the interior of the body are manifested on the surface of the body.Therefore, in the diagnosis of a disease, internal changes can be inferred by observing the outer appearance, and systematic changes can be discovered by the observation of a localized area; internal pathological changes of Zang-Fu organs, qi and blood can be detected by studying signs and external symptoms.For example, if we observe redness, swelling and pain in the eyes caused by a rise in the liver fire, then, during the diagnosis, attention must be paid to manifestations such as reddened face, taut pulse, bitter taste in the mouth, or seburra yellow on the tongue. In other words, will have to connect the local changes with the systemic changes and discover the nature of the disease by its signs and external symptoms.On the other hand, the manifestation of the disease is usually defined and influenced by the natural environment. Phenomena such as alterations in climate, the sudden cold, or other sudden attacks to the body lead to disease.Therefore, pay attention to the interrelationships between the environment and the internal environment. Search for causal factors based on differentiation and determine the treatment according to the etiology this principle represents the major points in the determination of the treatment based on the differentiation of syndromes.This is explained in the following two aspects: concepts of symptom, syndrome and disease – symptom: irregular manifestations of a disease, such as headaches, fever, sweating, and/or thirst.