Condensation nucleus

Condensation nuclei are fine particles, either solid or liquid, suspended in the atmosphere.

When they come into contact with these nuclei, atmospheric pollutants and water vapour molecules condense and accumulate. When the weight of the nucleus and its condensate becomes too heavy, it becomes visible and falls in the form of precipitation.

Condensation nuclei are therefore at the origin of cloud formation, rain and, in the case of freezing nuclei, hail and snow.