A cloud chamber is a sealed environment that allows scientists to observe the paths of charged particles, such as those produced by radioactive decay. It contains a supersaturated vapor, usually alcohol, which condenses into tiny droplets when a charged particle passes through, creating visible trails. These trails help researchers study the properties of particles and their interactions. Invented by Charles Thomson Rees Wilson in 1911, the cloud chamber has been instrumental in particle physics. It has contributed to the discovery of various subatomic particles, including muons and pions, enhancing our understanding of the fundamental forces of nature.