Interfaces in heterostructures often exhibit emergent physical properties that are absent in the constituent layers. Recent advances in fabricating atomically-defined interfaces have enabled us to design unique quantum properties through symmetry and electronic structure engineering. These heterostructures, together with their compatibility with nanofabrication, are promising for constructing functional quantum devices. I will illustrate the capability of such heterostructure engineering by taking two examples. First, I will explain our discovery of a versatile method for synthesizing ferroelectric materials from non-ferroelectric two-dimensional (2D) materials: by physically stacking two monolayer boron nitrides at controlled angles, novel types of ferroelectricity emerge at the interface. I will demonstrate its functionality as one of the world’s thinnest ferroelectric non-volatile memories at room temperature. As another example, I will demonstrate the versatile spintronic functionalities of topological insulator heterostructures synthesized by a thin film growth method. Finally, I will conclude by discussing how we can overcome the limits of existing heterostructure engineering for the future design of quantum materials and functionalities.