We say the cause of perfume disappearing is evaporation. Evaporation gets blamed for a lot of things people forget to put the top on. In looking at a drop of water under a microscope, we find there are twice as many H's as O's. I am not sure how clouds get formed. But the clouds know how to do it, and that is the important thing.
Water vapor gets together in a cloud.
When it is big enough to be called a drop, it does. Thunder is a rich source of loudness. Isotherms and isobars are even more important than their names sound. It is so hot in some places that the people there have to live in other places.