Bronchoscopy is a procedure that looks inside the lung airways. It involves inserting a bronchoscope tube, with its light and small camera, through your nose or mouth, down your throat into your trachea, or windpipe, and to the bronchi and bronchioles of your lungs. This procedure is used to find the cause of a lung problem. It can detect tumors, signs of infection, excess mucus in the airways, bleeding, or blockages in the lungs. It also can allow your doctor to take samples of mucus or tissue for other laboratory tests, as well as to insert airway stents, or small tubes, to keep your airway open to treat some lung problems.