Abstract: A method for providing a nanopattern of periodically ordered metal oxide nanostructures on a substrate is described. The method comprises the steps of providing a microphase separated block copolymer as a thin film on a substrate, the block copolymer comprising a first polymer having an affinity for a cations of the metal and a second polymer having a lower affinity for the cations than the first polymer, and selectively incorporating a salt of the metal cation into the first polymer of the block copolymer by means of a solvation process prior to or after formation of the microphase separated block copolymer. The block copolymer film is then treated to oxidise the metal ion salt and remove the polymers leaving a nanopattern of metal oxide nanostructures on the substrate.