Droplets and ice crystals behave somewhat like dust in the air made visible in a shaft of sunlight.
To the casual observer. dust seems to act in a totally random fashion. moving about chaotically without fixed direction. But in fact particles are much larger than water droplets and they finally fall. The cloud droplet of average size is only 1/2500 inch in diameter. It is so small that would take sixteen hours to a diameter of 1/125 inch or larger it can fall from the cloud. The average raindrop contains a million times as much water as a tiny cloud droplet. The growth of cloud droplet to a size e large enough to fall out is the cause of and other forms of precipitation. The important growth process is called “coalescence.”