Cumulonimbus clouds are tall and dense, and involved in thunderstorms and other intense weather. Cumulonimbus means "column of rain" in Latin. They form as a result of atmospheric instability. These clouds can form alone, in clusters, or along a cold front in a squall line. They create lightning through the heart of the cloud. Cumulonimbus clouds form from cumulus clouds (namely from cumulus congestus) and can further develop into a supercell, a severe thunderstorm with special features.