Lignin， a three-component bio-polymers formed through ether and carbon-carbon bonds， constitutes a three-dimensional network structure within woody tissues. Primarily found in wood tissues， it serves to harden cell walls by creating an interwoven network， forming the main component of secondary cell walls. Lignin is predominantly located between cellulose fibers， providing compressive strength. In woody plants， lignin accounts for 25% of total organic matter， ranking as the second most abundant organic compound globally. Since lignin naturally interacts with cellulose and hemicellulose to form lignin-carbohydrate complexes (Lignin-Carbohydrate Complex)， researchers currently lack methods to isolate intact lignin without structural degradation.

The Lignin Stain Kit (Phloroglucinol Method) uses phloroglucinol to develop color， and the lignified cell wall is red after staining. This staining method is a simple microchemical method for detecting lignin in plant cell walls. It fades over time and is therefore not suitable for long-term tableting.