A popular form of mid-nineteenth century photography that created and enhanced the illusion of depth in photographs. The technique involves making two images with separate lenses placed 2.5 inches apart and mounting them side-by-side on a stiff backing, mimicking the view of human eyes. These images could be viewed using a stereoscope in which the two images were placed. It was first described by Charles Wheatstone in 1832 and improved upon by David Brewster in 1849. From the Greek stereos, meaning “firm” and skopeo, meaning “to look.”