Create a sentence that describes the formation of a cloud.
Clouds form when water vapor in the air cools and condenses into tiny droplets or ice crystals, gathering together in large groups that become visible in the sky.
Complete the following task based on the instruction and optional input provided.### Instruction:
Create a sentence that describes the formation of a cloud.

### Output:
Clouds form when water vapor in the air cools and condenses into tiny droplets or ice crystals, gathering together in large groups that become visible in the sky.