by David Murphy
Clouds are made of water. When you look at a cloud, you're really looking at trillions of tiny water droplets (or ice crystals, if the cloud is high enough to occupy freezing air). The droplets are tiny and barely visible individually, but together, they become easy to see. Technically, there are also tiny bits of dust or other particulates at the center of the water droplets, but the vast majority of a cloud is made of water.