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. Clouds just keep circling the Earth around and around. There is not much else to do.
Water vapor gets together in a cloud.
When it is big enough to be called a drop, it does. When there is fog, you might as well not mind looking at it. Humidity is the experience of looking for air and finding water. When rain water strikes forest fires, it heckstingwishes them. Luckily it affects we of the humans unlike that.