Clouds form when water vapor condenses as liquid water onto particles in the Earth's atmosphere and are composed of billions of tiny water droplets or ice crystals, depending on how high they are in the atmosphere. The three basic patterns of clouds are cirrus (wispy), stratus (sheets, or layers) and cumulus (the fluffy, cotton ball-like ones). Clouds can form low to the ground (like stratus clouds), in the middle of the atmosphere (like altocumulus clouds) or high up (like cirrus clouds). Clouds can affect Earth's climate by either reflecting incoming solar rays back out to space or by absorbing and re-emitting infrared radiation coming from Earth's surface. Read the latest research on the various types of clouds and how clouds form below.