Mott insulator is a central concept in strongly correlated physics and manifests when the repulsive Coulomb interaction between electrons dominates over their kinetic energy. A tunable Mott insulator, where the competition between the Coulomb interaction and the kinetic energy can be varied in situ, can provide an invaluable model system for the study of Mott physics. In this talk, I will discuss a general route to engineer strongly correlated physics in two-dimensional moiré superlattices, and show the experimental realization of a tunable Mott insulator in the ABC stacked trilayer graphene (TLG)/hBN moiré superlattice. The moiré superlattice in TLG/hBN heterostructures leads to narrow electronic minibands and allows for the observation of gate-tunable Mott insulator states at 1/4 and 1/2 fillings. Interesting signatures of superconductivity are observed at low temperature near the 1/4 filling Mott insulating state in the TLG/hBN heterostructures. A topological Chern insulator with Chern number C = 2 and ferromagnetism are experimentally observed in the non-trivial band in trilayer graphene system, which makes it possible to study Mott, superconductivity and topological physics in one system.