 This review paper discusses the structures, compositions, and properties of lignin-carbohydrate complexes, LCC, present in biomass and in the products obtained via pre-treating biomass. LCC is a complex formed by the binding of lignin units to hemicellulose or cellulose molecules. The nature and amount of LCC linkages and lignin substructures affect the efficiency of pulping, hydrolysis, and digestibility of biomass. Different methods are used to extract, fractionate, and analyze LCC of biomass, pulp, and spent pulping liquors. The main perspectives and challenges associated with these technologies are discussed. LCC has promising applications in medicine due to its high antihive, anti-herpes, and antimicrobial activity. It can also be used as a precursor for the preparation of spherical bio-carriers. This article was authored by Dmitry Tarasov, Matthew Leach, and Petromfatehi.