Cirrus, cumulus, and stratus are the types of cloud. Cirrus clouds are very thin and white in colour. They are formed of ice crystals and give a feathery appearance. They are the highest clouds. Cumulus clouds are generally dense and with sharp outlines, developing vertically in the form of rising mounds, domes or towers, of which the bulging upper parts often resemble a cauliflower. Stratus clouds resemble fog and made up of almost equal layers. Occasionally, they are broken into patches separated by blue sky by the incoming wind. Stratus clouds are grey in colour.