Porcelain Lithophanes were originally developed in France in the early 19th century probably based on earlier Greek marble designs. They use a basic principle of light whereby the "thinner" the material the more light is passed through and the lighter the image appears. The technique lends itself well to 3D printing where the thickness of the material can be controlled to within a few microns. 

Using software to process the image and then in house developed algorithms to print a "relief" Lithophane, a dramatic image is revealed when illuminated from behind.