This website from the US National Toxicology Program presents microscopic images of rodent organs and non-neoplastic lesions. The atlas is organized by organ system and is subdivided into chapters, each covering a single organ. Each chapter comprises a set of sections, each describing a single lesion. Each section includes histopathologic descriptions, high-quality images, diagnostic guideline recommendations, and references (Environmental Health Perspectives 122:A76, March 2014). Registration not required.