Clouds are "a visible mass of particles of condensed vapor (such as water or ice) suspended in the atmosphere of a planet (such as earth) or moon" according to Merriam-Webster.
Earth's clouds are primarily made out of water, and you'll find them from the ground as fog all the way to altitudes up to 47 to 53 miles (76 to 85 km), where you'll find the rare noctilucent clouds. Most clouds, however, exist below 43,000 feet (13,100 m).
The formation of clouds requires the right combination of ingredients and conditions. There is always water in the Earth's atmosphere, so it's not just the presence of water that creates clouds. Continue reading from Space.com
The International Cloud Atlas expands upon this original classification system and includes the 10 cloud types below.
High-Level Clouds
Mid-Level Clouds
Low-Level Clouds
