A pulmonary nodule is a lesion less than 3 cm in diameter found in the lungs during imaging. Many diseases such as inflammation, bleeding, infection, allergy, tuberculosis, and tumors can manifest as pulmonary nodules on the lungs. Therefore, if nodules are found on the lungs they need to be classified and their nature determined. Pulmonary nodules can be classified into three categories depending on the density of the nodules: 1. Solid nodules, which are nodules with soft tissue density, and in which the images of blood vessels and bronchi are obscured by the lesion. Ground glass nodules are nodules that are faintly ground glass-like in the lung, with a slightly increased density compared to the surrounding lung parenchyma, and in which blood vessels and bronchial images are still visible. 3, partially solid nodules, also known as or sub-practice nodules or mixed nodules, which contain both ground glass density and solid components. The nodules can be classified according to their diameter: pulmonary nodules, nodules less than or equal to 3 cm in diameter; small nodules: less than 1 cm in diameter; micro-nodules: less than 5 mm in diameter. Most benign nodules have smooth margins and clear boundaries, and most patients have no clinical symptoms, and the common ones are pulmonary malformations, inflammatory pseudotumors, lymphocytic hyperplasia, and pulmonary nodular disease. Malignant nodules often have indistinct margins, burrs, lobarization, chest crinkling, and inflatable bronchial signs. Do not panic if you find a lung nodule, because more than 95% of lung nodules are benign. You need to go to the hospital to see a thoracic surgeon or imaging doctor for a reading, who will give professional advice such as scientific follow-up observation, review after treatment or surgery according to the shape of the nodule.