The wikipedia defines recursion as “(…)a method of defining functions in which the function being defined is applied within its own definition (…) a process of repeating objects in a self-similar way”. Point a mirror towards another mirror and look inside: that´s recursion.
The company Droste has used this method in the graphic design of their packaging with a success so as to give name to the “Droste Effect”, i.e. a picture of a board showing a picture of that board showing that picture of a board showing…
This said, I would like to point you to two sites where I have seen great Drosterisms:
First, take a look at www.josleys.com, which contains many examples and shows transformations of ordinary pictures into Drosterites. Within said page is an explanation of how Escher used this method together with a mathematical transformation to create the enigmatic painting “Print Gallery”, and you can read that “Prof. Hendrik Lenstra succeeded in unraveling the mathematical structure of the image”…
The second site I want to show you, http://escherdroste.math.leidenuniv.nl/ , devotes itself to explaining Prof. Lenstra´s work on the “Print Gallery”. The site is full of pictures and videos that not only unveil the secrets of the drawing, but also show how Drosterism works.
Warning! Watching the videos in the sites above could keep you entangled in an infinite loop of self-repeating paradoxes, ditto. 😛
Update 26.09.07
Escher´s Droste Print Gallery@Flickr;
Droste Effect Tutorial, same source.