What I find to be the most fascinating and wonderful part of these pictures are the pupils and how dark they are. I struggle to figure out the right comparison to the void the project. It really is quite stunning.
Another thing that i find to be absolutely fascinating about the eye is the way in which it functions. All of those tubes, all of that "gunk," as others here have put it, serve as muscles that extend or retract to control the amount of light that passes through. Such a complex system for what would seem like a very simple task.