Many materials in nature inherit their impressive functionalities from a synergistic combination of cellulose with other organic or inorganic materials. Our work in this area aims to develop the tools and the fundamental understanding that allow us to engineer biohybrid cellulose materials with properties that significantly enhance the functionalities of traditional cellulose materials. One specific research focus is the combination of cellulose with proteins. By using carefully synthesized colloidal nanocellulose particles, Cellulose Nanocrystals and Cellulose Nanofibrils, together with monomeric or aggregated proteins we are studying their supramolecular interactions and colloidal co-assembly into functional materials in the form of e.g. composite films, foams, hydrogels and aerogels. Another research focus is the electrostatically and entropically driven assembly of nanocellulose with conductive nanomaterials, e.g. silver nanowires, carbon nanotubes and MXene nanosheets, into hybrid materials with tunable electronic and optical properties. This work contributes to an improved understanding of bottom-up fabrication of cellulose-based materials and the applications that we target include food packaging, antimicrobial materials and lightweight multifunctional composites.