Nanocellulose in the form of cellulose nanocrystals or cellulose nanofibers (CNF) is a very active research field, with thousands of journal publications on the topic. Important industrial applications include paints, coatings, adhesives, cosmetics and other uses as thickening agent, filters and as dry strength agent in paper and board applications. Obstacles to increased use include cost, processing difficulties from high viscosity of nanocellulose colloids, and high cumulative energy demand, which means that the environmental impact from nanocellulose use can be higher than is desirable.
Chemical pulp fibers in the form of holocellulose wood pulp, can be prepared based on mild delignification and minimized mechanical damage. Such fibers show preserved cellulose nanostructure, rather than the collapsed cell wall of hornified, bleached kraft pulp. The mechanical fiber properties are therefore excellent so that strong, highly recyclable paper and hot-pressed, high-density composites can be prepared. Compared with nanopaper from CNF, the mechanical properties are only marginally lower, but at much lower cost and reduced energy demand. Chemical modification can be carried out readily by green chemistry approaches, so that corresponding polymer matrix composites show excellent properties.
Wood veneer can also be prepared by mild delignification so that the cell wall becomes nanoporous and properties dominated by nanocellulose. The orientation of the cellulose nanofibrils is another advantage of wood substrates, and top-down processing reduces energy demand. The cell wall can be functionalized by green anhydrides for moisture resistance, by clay nanoplatelets for fire retardancy, by plasmonic nanoparticles for structural color, by thermo- and photochromic particles, as electrochromic devices, by quantum dots for luminescence, by optical dyes for lasing purposes and by monomers for in-situ polymerization in the nanostructured wood cell wall. In our research, transparent wood is the most important research area, and many examples will be provided, as well as a discussion of how nanostructure is influencing light scattering.

Pulp fibers and wood as nanocellulose materials