Smoking may cause harm to many organs such as the brain, heart and lungs. 1. Brain hazards: Smoking reduces circulation in the brain, resulting in symptoms such as ischemia and hypoxia, causing occlusion of blood vessels in the brain, and may lead to stroke, mental decline, and so on. 2. Heart Harm: Carbon monoxide in cigarettes reduces the oxygen-carrying capacity of the blood. Long-term development will also affect the load capacity of the heart, leading to a variety of heart diseases, such as partial ischemia of the heart, acute myocardial infarction. 3. Lung damage: smoking will lead to shortening of the cilia of the bronchial epithelial cells, reducing local resistance, which can easily lead to tracheal, bronchial and lung infections. Smoking not only leads to the above damages, but also has a definite carcinogenicity, smoking and oral cancer, esophageal cancer, stomach cancer, lung cancer and other diseases have close correlation, it is recommended that smokers quit smoking as soon as possible.