Ectoin was discovered in the 1980s while studying extremophilic microorganisms, which can survive in particularly hostile environments such as deserts, salt lakes, or hot springs. To protect themselves from extreme heat, UV radiation, high salinity, and temperature fluctuations, these microorganisms produce Ectoin, a small molecule that stabilizes proteins and cell membranes and limits water loss. In cosmetics, we utilize this natural protective ability of the molecule to help the skin defend itself against daily external stressors (such as sun, heat, wind, pollution, cold, and temperature changes) and maintain long-term hydration. Thanks to its "hydration shield" effect, Ectoin contributes to preserving the elasticity and function of the skin barrier, making it particularly useful during periods of intense stress, such as summer, after sun exposure, or for easily irritated skin. Beyond its effectiveness, it is an ingredient well-tolerated even by the most sensitive skin, with no risk of stinging or irritation.