Dust, soot and bacteria are examples of condensation nuclei. Water vapor condenses and forms on these small particles, which causes rainfall. Condensation nuclei are commonly called cloud seeds.
Condensation depends on a nongaseous particle to use as a vessel for the liquid formed from water vapor. These particles are called cloud condensation nuclei.
Cloud condensation nuclei can be formed naturally, or they can be man-made. Water vapor can condense around pollution particles created by burning fossil fuels in factories. Water can also condense around sea salt, bacteria and volcanic ash, forming distinctive clouds. Each different cloud condensation nuclei has an effect on the composition and type of cloud that is formed from them.