The Siphonaptera

Great fleas have little fleas upon their backs to bite 'em, And little fleas have lesser fleas, and so ad infinitum. And the great fleas themselves, in turn, have greater fleas to go on; While these again have greater still, and greater still, and so on. [1872 A. De morgan Budget of Paradoxes 377]

One of my favorite poems that explains the fractal holographic nature of reality.