What is the principle of the Wilson chamber?

The Wilson chamber is a container with a glass lid and a piston at the bottom, filled with saturated vapors of water, alcohol or ether. The vapors are thoroughly cleaned of dust so that water molecules do not have condensation centers before the particles fly. When the piston is lowered, the vapors are cooled and become supersaturated due to adiabatic expansion. A charged particle passing through the chamber leaves a chain of ions on its way. The vapor condenses on the ions, making the particle track visible.