Mollusks such as the blue mussel (Mytilus edulis) secrete adhesive proteins that exhibit strong and reliable underwater adhesion. A key adhesive component in these adhesive proteins is an amino acid, 3,4-dihydroxyphenylalanine (DOPA), which is responsible for both interfacial binding and intermolecular cross-linking. DOPA is a unique and versatile adhesive moiety, capable of binding to both inorganic and organic surfaces through either strong reversible bonds or covalent attachment. This chapter reviews the chemistry of DOPA side chain and the use of DOPA and its derivatives (e.g., dopamine) as building blocks in developing mussel-inspired adhesives, coatings, and multifunctional polymeric anchors for various applications.