Metal-insulator transition (MIT) driven by many-body interactions is an important phenomenon in condensed matter physics. Exotic phases always emerge around the metal-insulator transition points where quantum fluctuations arise from a competition among spin, charge, orbital, and lattice degrees of freedom. Two-dimensional (2D) materials are a large class of materials. Their simple structure, low dimensionality, and highly tunable carrier density make them an ideal platform for exploring exotic phases. However, the many-body interactions are normally weak in most 2D materials, hence, the correlation-related phenomena attract little attention in the studies of 2D materials for a long period. Recently, people found that the many-body interactions can be enhanced in 2D hetrostructures or artificially-creased 2D structures. Correlation-related phenomena were found in many interesting systems, such as LaAlO3/SrTiO3, twisted bilayer graphene, etc.