A method for shaping keratin fibres comprising: providing a crosslinking composition, wherein the crosslinking composition comprises: an active agent, wherein the active agent is selected from the group consisting of: oxoethanoic acid, 2,2-dihydroxyethanoic acid, 2,2′-oxybis(2-hydroxy)-ethanoic acid, a derivative thereof, and mixtures thereof; and wherein the active agent has a molecular weight of 500 g/mol or less; a photocatalyst; a cosmetically acceptable carrier; and applying the crosslinking composition to keratin fibres, mechanically shaping the keratin fibres with an appliance or implement, and exposing the composition to electromagnetic radiation having a wavelength of from about 300 nm to about 750 nm. Also a related composition, use, kit and process.