Clouds consist of water droplets, lifted into the sky by the heated air. At the top is colder than the surface of the earth (why?), the air cools, the steam condenses.
But in the beginning of this process, the droplets need the smallest particles of dust, to which may be attached water molecules. They are called condensation grains. Even a perfectly clean air can be "saturated", that is to contain the excess water vapor, but they are not able to condense into droplets.
The clouds, the sun's rays pierced, look white, but often cloudy sky looks cloudy and gray. Then the clouds so dense, multi-layered, that stand in the way of sunlight.
The cloud may seem quite black, if it contains many particles of dust or soot, which often happens over industrial areas.
Clouds are formed in the space between the Ground surface and the upper troposphere (what's this?) approximately to the height of 14 km
There are three levels of the troposphere, where most often there are certain types of clouds are The highest between 7 and 14 km and consist of ice crystals. They look like delicate white veil, feathers or fringe and called Cirrus.
Cloud medium height can be observed between 2 and 7 km, they are composed of ice crystals and tiny raindrops. These include sheep, heralding a change in the weather, and solid gray layered clouds, promising a storm.
Low hanging clouds are located at an altitude of about 2 km and consist exclusively of water droplets. If the sky stretched torn veil stratocumulus clouds, the weather remains good, clear. But the same type are continuous and monotonous grey layered clouds that often sow drizzling rain, and layered rain, is always fraught precipitation.
Powerful Cumulus clouds satellites stable good weather. Sometimes they play the whole view: that resemble huge cauliflowers, an animal or even a human face.