The present invention provides a process for preparing a functionalised polymeric chromatography medium, which process comprises (I) providing two or more non- woven sheets stacked one on top of the other, each said sheet comprising one or more polymer nanofibres, (II) simultaneously heating and pressing the stack of sheets to fuse points of contact between the nanofibres of adjacent sheets, and (III) contacting the pressed and heated product with a reagent which functionalises the product of step (II) as a chromatography medium.