This is a lithophane of the famous Mona Lisa (La Gioconda) by Leonardo da Vinci.
When printed in FDM it's best to print on a side (upright) to benefit from the layer resolution, also PLA is better because of less warping. The one in the picture was printed upright in white PLA (0.15 mm layers) on a PP3DP Up! Plus. It's best to use opaque material like white or yellow, ABS is possible but will warp more because of the thin structure.
-->If people have a request for another lithophane (of any picture) just put it in the comments.<--