The Kelvin-Helmholtz cloud. Not a very snappy name. Needs a rebrand. This looks like a series of breaking waves, and it's caused by shearing winds the wind above the cloud layer and below the cloud layer differ significantly, and in the middle, in between, you get this undulating of the air, and if the difference in those speeds is just right, the tops of the undulations curl over in these beautiful breaking wave-like vortices. All right. Those are rarer clouds than the cirrus, but they're not that rare. If you look up, and you pay attention to the sky, you'll see them sooner or later, maybe not quite as dramatic as these, but you'll see them. And you'll see them around where you live. Clouds are the most egalitarian of nature's displays, because we all have a good, fantastic view of the sky. And these clouds, these rarer clouds, remind us that the exotic can be found in the everyday. Nothing is more nourishing, more stimulating to an active, inquiring mind than being surprised, being amazed. But you don't need to rush off away from the familiar, across the world to be surprised. You just need to step outside, pay attention to what's so commonplace, so every day, so mundane that everybody else misses it. One cloud that people rarely miss is this one: the cumulonimbus storm cloud. It's what produces thunder and lightning and hail. These clouds spread out at the top in this enormous anvil fashion, stretching ten miles up into the atmosphere. They are an expression of the majestic architecture of our atmosphere.