Cellulose fibres, cellulose nanofibers, cellulose nanocrystals and cellulose derivatives are all examples of cellulose-based materialsthat display superior characteristics with a number of desirable properties, including biodegradability, sustainability, biocompatibility, thermal properties , optical transparency, flexibility, high mechanical strength, high porosity,hydrophilicity, a large surface area and broad chemical modification capabilities. "Smart" materials based on cellulose created by the chemical changes and physical incorporation/blending techniques offer numerous advantages, most notably their intelligent responses to environmental stimuli. Conductive networks are formed in cellulose-based composite materials by combining or coating conductive materials with the cellulose components or by directly carbonising the cellulose materials. Numerous nanopaper-based optical sensing platforms are explained and how they can be tailored to exhibit plasmonic or photoluminescent features suitable for sensing applications using nanomaterials or as biomaterials. The responsiveness of these "smart" materials to pH, temperature, light, electricity, magnetic fields and mechanical forces, among other parameters, is also reviewed, as were their applications as drug delivery systems, hydrogels, electronic active papers, sensors, shape memory materials, smart membranes, etc.