The image structure and changes in image structure during deterioration of albumen prints, a silver printing-out paper extensively used in the 19th century, were investigated by use of transmission electron microscopy. Albumen print images are composed of roughly spherical particles with diameters ranging from less than three to approximately fifty nanometers, with most between five and twenty nanometers. The image material is concentrated in the upper half of the albumen layer. Various influences on image formation are discussed, including gold toning, which distorts the original particle into an elongated, irregular shape. Because of the photolytic mechanism of image formation, low-density areas have fewer and smaller particles than high-density areas, leading to rapid highlight density loss through an oxidativereductive deterioration process. The image structure and resistance to deterioration of albumen prints and a typical developing-out paper are compared. In high-density areas of albumen prints incubated at high RH, the image deposit is completely re-formed, underscoring the need to control the relative humidity of the storage areas for these objects. A means of predicting microstructural changes based on initial particle size, size frequency distribution, andspatial distribution is presented. For more information on albumen prints, see also AATA 17-1648, 19-1923, 19-1924, and 19-1925.