Steam explosion pre-treatment of biomass presents one of advanced technique for transformation and functionalisation of the components of natural polymers and allows to extract easily hemicelluloses and destructed fragments of lignin from the processed mass, if needed. Depending on the treatment severity the fibres of cellulose are reduced to micro-fibrils and nano-size whiskers. The complex physical and chemical modification proceeding at steam explosion pre-treatment of wood biomass is used to improve the properties of the diverse composite materials made of the renewable resource for a variety of purposes e.g. hemp and flax fibres for electro-spinning, hemp and flax shives as heat insulating composites. Considering bio-refineries based on biomass pre-treatment by steam explosion the effects of steam explosion severity on mass recovery and properties of processed wood biomass and composite products including self-binding fibreboards made thereof are presented and discussed with respect to applications. The paper includes published results and is kind of a review of the authors’ results reflecting the research directions.