AbstractPaper aging and conservation are matters of concern to those responsible for archives and library collections. Wood-derived fibers are mainly composed of cellulose, hemicelluloses, and lignin, but paper composition can also include additives, such as starch, minerals, and synthetic polymers. Therefore, paper is a multi-component material, and because of its complex and varied nature, research findings in paper chemistry can be difficult to interpret. Deterioration of paper is caused by many factors such as acid hydrolysis, oxidative agents, light, air pollution, or the presence of microorganisms. The origin of the cellulosic material, as well as pulping and papermaking procedures, additives, and storage conditions play a crucial role. The chemical changes occurring within paper thus involve multi-parameter processes. The purpose of this review, which mainly focuses on the most recent decade, is to provide a description of the more important changes produced by aging and an update of the new tools available for the study of paper deterioration and its conservation.