Low-altitude clouds, also known as stratiform clouds, are clouds that form at altitudes of up to 6, 500 meters. They are composed of water droplets or ice crystals and are usually found in the lower atmosphere. Stratiform clouds are generally divided into two categories: cumulus and stratus. Cumulus clouds are fluffy and often appear in the shape of a cotton ball, while stratus clouds are flat and layered. Low-altitude clouds are important for regulating the Earth's climate, as they reflect sunlight and help to cool the planet.