Block copolymers, a class of macromolecules composed of two or more chemically distinct polymer blocks, exhibit complex self-assembly behaviors at the molecular scale. These materials, which are found in various everyday products such as upholstery foam, adhesive tape, and asphalt additives, can form intricate nanostructures due to the thermodynamic incompatibility of their blocks. The unique properties of block copolymers, characterized by fluid-like disorder on the molecular scale and ordered structures at larger scales, make them useful in applications ranging from polyurethane foams to medical implants. Recent advances in synthetic chemistry and statistical theory have enabled the precise control over the morphology of block copolymers, leading to the development of novel molecular architectures with tailored physical properties. Theoretical models, particularly mean-field theories, have been developed to predict the domain shapes, dimensions, and connectivity of block copolymers based on their composition and molecular architecture. These theories have been validated through experimental studies, demonstrating their ability to predict complex microphase structures such as lamellae, cylinders, and gyroids. The article also discusses the challenges and opportunities in exploring block copolymers with more than two distinct blocks, highlighting the increased complexity in phase behavior and the potential for creating new materials with diverse applications. Despite the progress, significant areas of research remain, including the exploration of block copolymers with four or five blocks and their industrial applications as emulsifiers and additives in polymer alloys.Block copolymers, a class of macromolecules composed of two or more chemically distinct polymer blocks, exhibit complex self-assembly behaviors at the molecular scale. These materials, which are found in various everyday products such as upholstery foam, adhesive tape, and asphalt additives, can form intricate nanostructures due to the thermodynamic incompatibility of their blocks. The unique properties of block copolymers, characterized by fluid-like disorder on the molecular scale and ordered structures at larger scales, make them useful in applications ranging from polyurethane foams to medical implants. Recent advances in synthetic chemistry and statistical theory have enabled the precise control over the morphology of block copolymers, leading to the development of novel molecular architectures with tailored physical properties. Theoretical models, particularly mean-field theories, have been developed to predict the domain shapes, dimensions, and connectivity of block copolymers based on their composition and molecular architecture. These theories have been validated through experimental studies, demonstrating their ability to predict complex microphase structures such as lamellae, cylinders, and gyroids. The article also discusses the challenges and opportunities in exploring block copolymers with more than two distinct blocks, highlighting the increased complexity in phase behavior and the potential for creating new materials with diverse applications. Despite the progress, significant areas of research remain, including the exploration of block copolymers with four or five blocks and their industrial applications as emulsifiers and additives in polymer alloys.