Method of identifying and using compounds which inhibit the expression or activity of micro-RNAs for preventing and/or attenuating ageing, and/or for hydrating skin. An in vitro method for screening for candidate compounds for preventing and/or attenuating ageing of the skin, and/or for hydrating the skin, includes the following steps: a. bringing at least one test compound in contact with a sample of keratinocytes; b. measuring the expression or the activity of at least one microRNA in the keratinocytes; c. selecting the compounds for which an inhibition of at least 20%, preferably at least 30%, preferably at least 40% of the expression or an inhibition of at least 20%, preferably at least 30%, preferably at least 40% of the activity of at least one microRNA is measured in the keratinocytes treated in a. compared with the untreated keratinocytes.