Inclusion Criteria:  Patients with pulmonary nodules ≤ 3cm Patients who provide electronic, written or oral consent to be enrolled in the follow-up cohort  Exclusion Criteria:  Patients with a surgical history of pulmonary nodules; Patients who have obtained pathological diagnosis through surgery or non-surgical methods such as puncture; Patients with pulmonary nodules that are likely metastatic from other sites; Refuse to participate in this study.