Nonalcoholic fatty liver disease (NAFLD) is a term currently applied to accumulation of triglycerides in the liver which is observed microscopically as "macrovesicular" steatosis. The term applies to the full range of liver parenchymal injury from "simple steatosis" to "steatohepatitis" with or without fibrosis. This article discusses the full histopathologic spectrum of NAFLD. Additionally, the summary includes an historical overview as well as contemporary thoughts on the significance of the process(es). While largely focused on adult NAFLD, the manuscript also summarizes what has been reported to date for NAFLD in the pediatric population.