Standing at the edge of the world.
At microscopic scales, even a clean break isn’t very clean - this electron microscope picture is of the edge of a piece of glass, on which I had fabricated a long wall of semiconductor (the long columned wall you see at the middle right). I had zoomed in on this spot to make sure the wall went all the way to the edge of the glass. What I didn’t expect to see were these little guys clustered near the edge, seeming to look out over into the abyss. They were probably formed by little bits of debris (their little hats), that flew from the edge when it was cut. Since I made the nearby wall by etching away all of the semiconductor that wasn’t protected by a glassy wall-shaped mask, the same etching process left behind all the areas that were protected by the little debris hats. They’re small - if you stacked 200 of them on top of each other, they’d just about equal the thickness of a single human hair.