Complex made of silicon organic derivative (I) associated with one or more calibrated fragments of hyaluronic acid having a molecular weight of 150-750 kDa, by weak bond, is new. Complex made of silicon organic derivative of formula (R xSi(OH) 4 - x) (I) associated with one or more fragments calibrated by hyaluronic acid having a molecular weight of 150-750 kDa, by weak bond, is new. R : 1-4C alkyl and x : 1 or 2. ACTIVITY : Dermatological. MECHANISM OF ACTION : None given.