Episode 20: Zeste de science presents a new episode of Ecorce de recherche, an immersion into archives of last century's scientific research. The human eye cannot detect the movements of transparent and isotropic media such as air. In 1954, scientists put light properties to good use and developed a new device that enabled them to see such media. Via this device, they could divide a beam into different wavelengths. The resulting colours make it possible to see the movements of air or water, along with the variations of thickness in a seemingly flat piece of glass. This technique could be applied in various fields: physics, biology, and even art.