Most people probably don't notice it, but on a cloudless day, you lie down and fix your gaze into the sky, pay attention to all sorts of motion inside and on your eye. For example, you should be able to see various shapes sail smoothly through your point of view. If you move your eyes, the shapes seem to follow, but imperfectly. These shapes are specks of dust, lashes, and other tiny particles that settled on your eyeball. Because they are so close to the lens, they are so out of focus that you see them as much thicker than they actually are, with a halo around them (just like you would in a microscope, looking at something out of focus). They sail across your view because they are slowly sliding down a fluid surface of your eye. They follow your eyes because they are fixed to the eyeball, but not perfectly, because of friction.
I like to play a game, focusing on a particular speck of dust (maybe the one with the most interesting shape) and moving my eyes around to make sure that the speck stays in the center of my vision, motionless, and doesn't slide off. It's an interesting exercise in navigation where the mechanics are unlike anything I've experienced.
Attention to detail reveals complexity you may never have imagined.