Take a look at the sky on any given day and you’ll likely see clouds of different shapes — some look like cotton balls, others are fine and feathery or tall and imposing. For instance, cumulus clouds (from the Latin for “heap”) resemble a pile of cotton balls, while stratus clouds (meaning “layer”) stretch out like blankets and cirrus clouds (Latin for “hair”) look feather-like. Air temperatures decrease with altitude, so clouds that form closer to earth are made mostly of water droplets, while higher clouds tend to be composed of ice crystals. This difference in composition influences how clouds look: water-based clouds, like cumulus, have crisp edges and a solid appearance, while icy clouds, such as cirrus, are usually more transparent and diffuse. These winds act on the ice crystals that make up cirrus clouds, twisting and spreading them into delicate strands.