Light micrograph of diffuse alveolar lung damage. Diffuse alveolar damage (DAD) of the lung is a form of severe injury also known as acute respiratory distress syndrome (ARDS). The histologic hallmark of DAD is the formation of hyaline membranes, which are seen here as the light pink bands surrounding alveolar spaces (white). Haematoxylin and eosin stained tissue section. Magnification: x200 when printed at 10cm.