Nanocelluloses are renewable and sustainable answers to some of the emerging demands of bioeconomy in the future. They have been well utilized at their colloidal form to create many different materials, including filaments, films, hydrogels, etc. Among these applications derived from nanocelluloses, the remarkable opportunities of using nanocelluloses in the formulation of multiphase systems via Pickering stabilization are introduced in this work. Two types of nanocelluloses, cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF), are firstly deployed to produce Pickering emulsions, and their differences on emulsion properties considering their morphogenesis, interfacial activity and the ability to network and self-assemble in aqueous phase are revealed accordingly. To obtain nanocellulose-stabilized multiphase systems with long-term stability, the combination of CNC and CNF, where CNC stabilizes the oil-water interfaces and CNF modulates the microstructure of the aqueous phase, has exhibited great potential to enable a super-stable multiphase system with over 7-month stability. Moreover, surface modification through controllable electrostatic interaction between nanocelluloses and cationic agents is developed to further enhance the interfacial adsorption of nanocellulose in situ. This particularly applies to CNF where its interfacial adsorption behavior can be altered, displaying a dynamic change from freely dispersing in the aqueous phase, over partial covering the interfaces, to finally fully cover the droplets. Exploiting the uniqueness and robustness of nanocellulose-based Pickering emulsions, two applications using nanocellulose multiphase systems are developed in this work. The first one is to use the strong protection capability of nanocelluloses and Pickering stabilization to achieve controllable lipid digestion control in a simulated gastrointestinal tract. CNC-stabilized Pickering emulsions show a strong effect on the restriction of lipid digestion, which shows great opportunities on formulating functional foods, particularly for delivery of bioactive components cross stomach. Another application is to exploit the phase-separation nature of multiphase system to modulate the liquid crystal assembly of CNC. The produced CNC-based water-in-water emulsions exhibit a capability to control the assembly of CNC in each phase separately via finetuning the osmotic pressure of each phase, which provides guidance for CNC assembly in a less strict condition. The long-term goal of this research is to adopt nanocellulose-based multiphase systems in value-added, high-end, multifunctional products under the concept of “wood-for-bioeconomy”.