A 3mm ground glass nodule in the lungs with indistinct margins and light density means that the lung nodule is microscopic and in most cases is benign and not harmful. Tuberculosis, inflammation, tumors, etc. can cause ground glass nodules. Generally speaking, ground glass nodules in the lungs do not have any symptoms, if the nodule is less than 5mm, most of them are benign, can be observed clinically, do not need to follow up, regular review can be to see whether the nodule grows, if there is a phenomenon of growth, it is necessary to treat in a timely manner. If the nodule grows, timely treatment will be needed. If the nodule is multiple, it may cause chest pain, chest tightness, dyspnea and coughing, etc., and should be examined in the hospital for a clear diagnosis. Note: Patients with ground-glass nodules in the lungs need to quit smoking and drinking, eat less pickled food, and eat more food containing vitamins and trace elements.