Abstract: A process is disclosed for pretreating a solid, cellulose-containing biomass material. The pretreatment comprises contacting the solid biomass material with an Ionic Liquid medium under sub-solvating conditions. The pretreatment results in an opening up of the texture of the solid biomass material, while no or a limited amount of biomass material is dissolved. The Ionic Liquid medium preferably is an inorganic molten salt hydrate. The pretreated biomass material can be as a feedstock in any process that benefits from the change in texture resulting from the pretreatment.