When it comes to ground glass shadow in the lung, people are very worried that it may be lung cancer. What is ground glass, ground glass is the seemingly clear glass seen on the washroom door, less than 3cm we call it a lung nodule. A ground glass nodule is an imaging concept or description. Ground glass nodules are generally divided into pure ground glass nodules and mixed ground glass nodules. Among these nodules, nodules below 5mm are basically considered benign and can be followed up once a year; between 5-8mm the malignancy rate is only 1% and can be followed up once every six months; over 8mm need to be followed up once every 3 months and the malignancy rate is 15% for 8-20mm; and nodules larger than 20mm will have a higher malignancy. The overall malignancy rate of nodules found on physical examination is only about 4%, and the overall probability of malignancy of mixed type ground glass nodules is higher than that of pure ground glass nodules. The follow-up is mainly to observe the changes in the size, density and morphology of the ground glass shadow. If the ground glass shadow is observed to increase significantly, the density becomes solid, or there are burrs, lobes, or blood vessels penetrating it, you need to be especially alert to the possibility of malignancy. The grinding glass nodule is actually not terrible, and its overall slower growth rate allows us more time to identify his benign and malignant possibilities and take appropriate treatment to eradicate it.