This document discusses the mosaic pattern seen on CT scans of the chest. It describes how the pattern shows areas of increased and decreased density that correspond to areas of ground glassing and air trapping, respectively. The black areas represent air trapping and can be seen in conditions like bronchiolitis obliterans, sarcoidosis, and asthma. The white areas represent ground glassing and alveolitis/pneumonitis, seen in diseases like desquamative interstitial pneumonia and nonspecific interstitial pneumonia. The mosaic pattern results from airway disease causing air trapping or alveolitis/pneumonitis causing ground glassing.