Three Spheres II
Three Spheres II is a lithograph print by the Dutch artist M. C. Escher first printed in April 1946. As the title implies, it depicts three spheres resting on a flat surface. The sphere on the left is transparent with a photorealistic depiction of the refracted light cast through it towards the viewer and onto the flat surface. The sphere in the center is reflective. Its reflection is a self-replicating image of Escher in his studio drawing the three spheres. In the reflection one can clearly see the image of the three spheres on the paper  Escher is drawing on: in the center sphere of that image, one can vaguely make out the reflection of Escher's studio, which is depicted in the main image. This process is implied to be infinite, recursive. The sphere on the right is opaque and diffuse, i.e. neither specularly reflective nor transparent. The painting is in the Escher Museum in The Hague.