This document discusses aspergillosis, a fungal infection caused mainly by Aspergillus fumigatus. It describes the morphology of the fungus, including septate hyphae that branch at acute angles. There are three main types of aspergillosis: invasive aspergillosis, which occurs in immunocompromised patients and can disseminate systemically; allergic bronchopulmonary aspergillosis, which affects patients with asthma; and aspergilloma, where the fungus colonizes preexisting lung cavities and can cause infection or hemoptysis.