The images show Hematoxylin and Eosin-stained cervical lesions. On the left hand side is shown a tissue section of low-grade disease (CIN1 (cervical intraepithelial neoplasia 1) (LSIL; low-grade squamous intraepithelial lesion)). On the right hand side is shown a tissue section of high-grade disease (CIN3 (HSIL; high-grade SIL)). Nuclei are stained purple, cytoplasms are stained pink. The granular, spinous, and basal layers are indicated for CIN1. A typical koilocyte is indicated with an arrow. The approximate extend of the significantly expanded basal compartment in CIN3 is indicated. Progression from CIN1 to CIN3 is due to persistent infection and up-regulation of E6 and E7 oncoprotein expression. A bullet point list of features of each stage of disease is beneath each image. A bullet point list of factors contributing to cervical-disease progression is shown beneath the purple block arrow.