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: 2-hydroxypropane-1,2,3-tricarboxylic acid, 1,2,3,4-butanetetracarboxylic 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 at a temperature of from about 80° C. to about 180° C. 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.