Why the cloud does not come …

As air rises and cools, water condenses from the vapor to the liquid state. If the temperature is below the freezing point, then ice crystals are formed instead. Condensation requires a seed called a condensation nucleus around which the water molecules can attach or nucleate themselves. Particles of dust floating in air can act as condensation nuclei; particles containing ions are effective nuclei because the ions electrostatically attract the polar-bonded water molecules.

The diameters of these particles range from 0.001 to 10 micro m and the particles are known as aerosols. For comparison, the size of an atom is about 0.0001 micro m, so the smallest aerosols may be composed of just a few hundred atoms.

Moisture + Aerosols (or a holding media), and cloud formation takes place.

Now what falls?

The tiny droplets grow by condensation and impact with their neighbors as they are carried by turbulent air motion, until they become large enough so that the force of gravity over comes that of friction and they begin to fall.

This rain drops further increase in size as they hit other droplets in the fall path.Therefore, a cloud as one piece will never fall like an Apple on Newton's head.