Abstract: Based on important advances over the last few decades, block copolymers have been established as an excellent physical model system for studying molecular self-assembly and related fundamental phenomena. Good agreement between the quantitative theory and accurate experiments on the equilibrium phase behaviour of block copolymers has been achieved, and a thorough understanding has emerged by connecting the microscopic constituents to the mesoscopic phase structures and macroscopic material properties. Here, we review our current understanding of block copolymer phase behaviour, the standard model with its underlying assumptions, and present an overview of future applications in various fields such as physics, chemistry, biology, and engineering.