Suggested are new extracts of microalgae selected from the group consisting of Thalassiosira sp. obtainable by treating said microalgae with a solvent selected from the group consisting of C 1 -C 4 aliphatic alcohols, ethyl acetate, water or their mixtures, removing the dissolved extracts from the residues and recovering the pure extracts from the solvent. The extracts show excellent properties particularly in modulating the metabolism of human skin and hair follicles.