Lithophane

A lithophane is an etched artwork, usually in porcelain that has been cast in the the design of detailed images that only truly reveal themselves when they are back lit.

A lithophane is completely different from two-dimensional engravings which are "flat", it's a 3D representation. The idea is relatively old and although the techniques have changed over time, it is gaining popularity again with advent of easy 3D printing technologies. Originally, an artist would create a shallow 3D image in wax which was then used to create a porcelain negative. When light passed through it, the image would come to life, looking like it was popping right off the stone. Today, 3D printers and etching machines are used to create often photo-realistic lithophanes.

Since the images change characteristics depending on the light behind them, they are more interesting than a two-dimensional picture. These Lithophanes hence can be used in a number of interesting ways- from plaques to be hung in windows, to lamp shields.

Here, have a look at one made by FORM3D Solutions, a product design firm based in Pune.

Source : Wikipedia