A stereograph is a pair of photographic images taken with lenses at slightly different angles. When viewed separately through a device called a stereoscope–one image for each eye–stereographs, like the one shown above, provide the illusion of normal depth perception and three-dimensional viewing. Stereographs were first developed as parlor entertainment in the 1840s, but did not enjoy widespread appeal until the 1860s. By the late 19th century, stereoscopes were common in middle-class drawing rooms, with educational, travel-oriented scenes being the most popular.