Abstract: Cellulose fibres in the nanometre length scale, more commonly known as nanocellulose, is intensively researched over the last three decades as reinforcement to produce high performance sustainable composites. The major driver for utilising nanocellulose as reinforcement is the possibility of exploiting the high stiffness and strength of cellulose crystals. Theoretical calculations and numerical simulations estimated the stiffness and strength of cellulose crystals to be ~180 GPa and ~22 GPa, respectively. Experimentally, Raman spectroscopy and X-ray diffraction have shown that nanocellulose possesses a tensile modulus of between 100-160 GPa. The tensile strength of nanocellulose was estimated to be ~1 GPa based on experimental results for elementary plant fibres. This talk will highlight research into utilising nanocellulose as reinforcement for polymers. We will start our discussion with using well-consolidated nanocellulose network (more commonly known as cellulose nanopaper) as 2D reinforcement for the production of optically transparent and high-performance composites for impact protection. This talk will also discuss the use of nanocellulose as binder through the cellulose "hornification" effect (i.e. hydrogen bond formation between adjacent nanocellulose) to upgrade loose or waste fibres into rigid and robust preforms suitable for structural and semi-structural applications.