The chapter discusses the structure and function of five major classes of plant cell wall proteins: extensins, glycine-rich proteins (GRPs), proline-rich proteins (PRPs), solanaceous lectins, and arabinogalactan proteins (AGPs). These proteins are complex carbohydrates, proteins, and other substances that contribute to the structural and functional diversity of plant cell walls. The chapter highlights the dynamic nature of these walls in growth, development, environmental sensing, signaling, defense, and intercellular communication. Extensins are hydroxyproline-rich glycoproteins (HRGPs) found in dicots and monocots, characterized by their high content of hydroxyproline, serine, and valine, tyrosine, lysine, and histidine. They form a polyproline II helical structure and are involved in cell wall strengthening and defense mechanisms. GRPs are characterized by their repetitive primary structure, containing up to 70% glycine arranged in short amino acid repeat units. They are found in both dicots and monocots and are involved in vascular development and stress responses. PRPs are another class of HRGPs, characterized by the repeating occurrence of Pro-Pro repeats. They are involved in various developmental processes and may play a role in nodule formation and bacterial infection. Solanaceous lectins are unique plant lectins found in solanaceous plants, characterized by their ability to agglutinate N-acetylglucosamine oligomers and their unusual amino acid and carbohydrate composition. They are involved in cell-cell interactions and wound healing. AGPs are highly soluble and glycosylated HRGPs, rich in hydroxyproline, serine, alanine, threonine, and glycine. They are involved in cell-cell recognition and may play a role in floral histogenesis and differentiation. The chapter also discusses the regulated expression and intermolecular interactions of these proteins, as well as their potential functions in plant development and defense. Future research directions include identifying new wall proteins, studying their functions, and understanding their evolutionary relationships.The chapter discusses the structure and function of five major classes of plant cell wall proteins: extensins, glycine-rich proteins (GRPs), proline-rich proteins (PRPs), solanaceous lectins, and arabinogalactan proteins (AGPs). These proteins are complex carbohydrates, proteins, and other substances that contribute to the structural and functional diversity of plant cell walls. The chapter highlights the dynamic nature of these walls in growth, development, environmental sensing, signaling, defense, and intercellular communication. Extensins are hydroxyproline-rich glycoproteins (HRGPs) found in dicots and monocots, characterized by their high content of hydroxyproline, serine, and valine, tyrosine, lysine, and histidine. They form a polyproline II helical structure and are involved in cell wall strengthening and defense mechanisms. GRPs are characterized by their repetitive primary structure, containing up to 70% glycine arranged in short amino acid repeat units. They are found in both dicots and monocots and are involved in vascular development and stress responses. PRPs are another class of HRGPs, characterized by the repeating occurrence of Pro-Pro repeats. They are involved in various developmental processes and may play a role in nodule formation and bacterial infection. Solanaceous lectins are unique plant lectins found in solanaceous plants, characterized by their ability to agglutinate N-acetylglucosamine oligomers and their unusual amino acid and carbohydrate composition. They are involved in cell-cell interactions and wound healing. AGPs are highly soluble and glycosylated HRGPs, rich in hydroxyproline, serine, alanine, threonine, and glycine. They are involved in cell-cell recognition and may play a role in floral histogenesis and differentiation. The chapter also discusses the regulated expression and intermolecular interactions of these proteins, as well as their potential functions in plant development and defense. Future research directions include identifying new wall proteins, studying their functions, and understanding their evolutionary relationships.