a tremendous attention owing the possibility for "on demand" engineering employing functional groups able to sense external stimuli such as pH, [5][6][7][8][9] light, [10][11][12] enzymes [13,14], and gases. [15,16] Among the advantages of these advanced materials, the most remarkable ones are the possibility to precisely control their disassembly processes in a spatiotemporal fashion, [12] and the ability to promote morphological transformations. [17,18] These features have made them a thriving research field in recent years, and attractive materials for important applications such as catalysis, biomedicine, or food technology have been developed. [19][20][21] However, most of these materials are derived from fossil resources and often are poorly biodegradable, [22] which together with the concerns about associated greenhouse gas emissions suggest that renewable polymers should play a crucial role in the development of the next generation of polymeric nanoparticles. In fact, macromolecules from renewable and abundant plant biomass are gaining a major role in the efforts to transition to a sustainable materials economy. [23][24][25] Among them, the aromatic plant polymer lignin is one of the most promising bio-based raw materials. [26][27][28][29][30][31] In this sense, lignin nanoparticles (LNPs) are postulated as prime platform for the development of stimuli-responsive nanoparticles. [32][33][34] In recent years the classical disdain on ligninbasically viewed as a byproduct from the pulp and paper industry and destined to be combusted -has given way to a paradigm shift towards the development of lignin-based advanced materials, supported by the inherent properties such as biodegradability, antioxidant activity, and absorbance of UV radiation which are preserved in LNPs. [35][36][37][38][39] In contrast to bulk lignin, LNPs resist aggregation in aqueous dispersions (pH 3-9) owing to their spherical shape and colloidal stability generated by the electrostatic repulsion forces mainly stemming from carboxylic acid and phenolic hydroxyl groups located on the surface of the particle. [40][41][42] This anionic surface charge has been exploited for physical modification of LNPs via adsorption of positively charged polyelectrolytes such as enzymes and polymers for a wide range of applications ranging from biocatalysts to composites among others. [43][44][45][46][47] Here, it is important to note that even one of the main limitations of LNPs, which arises from their dissolution in basic conditions (pH > 9) and aggregationThe design of stimuli-responsive lignin nanoparticles (LNPs) for advanced applications has hitherto been limited to the preparation of lignin-grafted polymers in which usually the lignin content is low (<25 wt.%) and its role is debatable. Here, the preparation of O 2 -responsive LNPs exceeding 75 wt.% in lignin content is shown. Softwood Kraft lignin (SKL) is coprecipitated with a modified SKL fluorinated oleic acid ester (SKL-OlF) to form colloidal stable hybrid LNPs (hy-LNPs). The hy-LNPs with a SKL-O...