A stereoscope is an optical device that allows users to view two slightly different images of the same scene, creating a three-dimensional effect. This device typically consists of two lenses and a viewing platform where the images are placed. When viewed through the lenses, the brain combines the two images, resulting in a perception of depth. Originally popular in the 19th century, stereoscopes were used for entertainment and education, showcasing landscapes, architecture, and other scenes. They played a significant role in the development of 3D photography and are related to modern technologies like virtual reality and 3D movies, enhancing visual experiences.