Escher wanted to show the illusion of a drawing as directly as he could. It looks like two threedimensional hands are drawing each other on a piece of paper. Which, in turn, is drawn on another piece. I wonder : would this be Eschers hand, and the pen he was using at the moment ?
A visitor in a museum is looking at a print. On this print you can see a boat steaming alongside a city. If you follow the houses of the city to the right, you come to a gallery . . . In which our young man is looking at the print. A self-containing picture ! A nice trivia is that the gallery shows prints from Escher.
This is an old and quite famous example of a self-referencing / self-containing image. This was the design for a box of Dutch cocoa. On the box is a nurse carrying the same box. And on that box we see the nurse again ... and so on.