Answer :

1.       All clouds are made up of tiny ice crystals or small water droplets that form together with a dust on the atmosphere.
Cirrus, cirrostratus and cirrocumulus are made up of ice crystals. It forms when the water vapor goes condensation at high altitudes in where the pressure on the atmosphere reaches the point from 600 mbar at 4000 meter above the sea level up to 200mbar at 12 000m above sea level. These clouds form thunderstorms, cyclones and contrails (a manmade cloud).