 Alginate is a natural polysaccharide with excellent biocompatibility and biodegradability that has many applications in biomedicine, including wound healing, cartilage repair, bone regeneration, and drug delivery. It can be easily modified to obtain derivatives with various structures, properties, functions, and applications through chemical and physical reactions, combination with other biomaterials, immobilization of specific ligands, and physical or chemical crosslinking. This article was offered by Jinchen Sun and Huaping Tan.