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Cellulose-lignin interactions denote the physical and chemical associations between cellulose microfibrils and the polyphenolic lignin polymer within the plant cell wall matrix, predominantly in secondary cell walls where both biopolymers are abundantly co-deposited ^[1]. These interactions encompass two principal categories: covalent linkages and non-covalent associations. Covalent bonds between lignin and cellulose occur through lignin–carbohydrate complexes (LCCs), wherein lignin units form direct chemical bonds with cellulose or, more commonly, with intervening hemicellulose molecules that bridge the two polymers ^[1]. The covalent linkages include benzyl ether and benzyl ester bonds formed during lignin polymerization, in which reactive lignin intermediates couple with carbohydrate hydroxyl groups ^[2]. Non-covalent interactions comprise hydrogen bonding between lignin phenolic and aliphatic hydroxyl groups and cellulose surface hydroxyls, hydrophobic associations driven by the aromatic nature of lignin and the relatively hydrophobic cellulose (100) crystal face, van der Waals forces, and physical entanglement of lignin chains within the polysaccharide network ^[3]. The heterogeneity of lignin—arising from its non-enzymatic, free-radical polymerization of monolignols—confers considerable variability in the nature and strength of cellulose-lignin contacts, with binding affinity modulated by lignin methoxylation patterns, oligomeric size, and aromatic ring orientation ^[3]. Unlike lignin–hemicellulose interactions, which are extensively characterized as discrete LCC fractions, direct cellulose-lignin contacts were historically presumed to be predominantly physical; however, contemporary molecular evidence confirms that covalent cellulose-lignin linkages also contribute to the structural integrity of the cell wall matrix ^[2]. The most prevalent covalent linkage is the benzyl ether bond, formed between the benzylic carbon of a lignin unit and a hydroxyl group on the carbohydrate chain. Benzyl ester linkages also occur, typically involving the carboxyl groups of glucuronic acid residues in hemicelluloses. These covalent bonds provide a robust chemical tether that anchors the lignin polymer to the cellulose-hemicellulose network, preventing the dissociation of the matrix components under physiological conditions. ^[1].