Nociceptors are subcutaneous, small nerve endings that cause pain receptors, and there are also more distribution of nociceptors in the internal organs. Many people think that pain is not a good thing, in fact, pain is the evolution of human beings in order to protect the safety of effective reflexes, such as encountering the fire hand will hide, encountered can damage their own things will be avoided, to avoid danger, to ensure their own safety. There are more painless patients, often do not live to adulthood will suffer more accidents, injuries, because they do not know the danger of avoidance and life-threatening. Pain is also an indicator of some diseases, most people go to the hospital because of pain, the symptoms of pain can indicate a problem in a certain area.