No one except perhaps a doctor understands the physical and mental effects of long, constant, unbearable pain …… , a torment that perverts the human personality. The meek become violent, the strong become weak, and even the most tenacious do not appear quieter than the most hysterical girls. I. What is pain? In 300 B.C., Egypt, India and other countries believed that pain was the “devil”, the punishment of God or the gods to human beings. In the 19th century, sensory neuropsychology recognized the sensory aspect of pain, and in the 20th century, pain was recognized as consisting of sensations and emotions. It was only in the 1970s that the nature of pain – the multidimensional nature of pain – was gradually revealed. ◎ Sensory-discriminative ◎ Motivational-emotional ◎ Cognitive-evaluative. Second, the definition of pain. International Academy of Pain (IASP, 1979): Pain is an unpleasant sensory and emotional feeling accompanied by existing or potential tissue damage. Pain is subjective, and each person learns the exact words to express it early in life through the experience of injury. It is a local or overall sensation in the body. Third, the classification of pain. Pathological classification: 1. Superficial pain: pain in the skin and mucous membranes due to injurious irritation. It is characterized by well-localized, limited, mostly sharp pain like pinprick-knife cut and produces muscle activity. 2. Deep pain: pain arising from ligaments, tendons, joints, fascia, thoracic and abdominal membranes, internal organs, etc. It is mostly a dull pain with imprecise localization, and the pain may have dispersion, or appear as a sensory allergy area. 3, neuropathic pain: can occur in any part of the nervous system lesions. Burning-like, intense diffuse and persistent, may have nociceptive hypersensitivity, unusual pain, etc. 4, psychogenic pain: psychogenic, can be accompanied by anxiety, depression, fear, etc., worth noting.