An actual cloud is a cumulation of water found in the that has condensed around condensation nuclei. There are three distinct forms of clouds: stratus, cumulus, and cirrus. Stratus clouds are long and flat and blanket the sky in a uniform grey. Cumulus clouds are puffy—like cotton balls. Cirrus clouds are thin and wispy. Cirrus clouds are only found in the highest regions of the troposphere, whereas stratus clouds and cumulus clouds are found on all three levels of the troposphere. Clouds do not form in the layers above the troposphere.