Control of the interlayer twist of van der Waals (vdW) interfaces has been widely used to engineer an arti?icial 2-dimensional (2D) electronic systems by the formation of a moiré superlattice. Many exotic physical phenomena occur associated with the incommensurability of the moiré superstructures where the wealth of the nontrivial topology of electronic band structures plays a key role to create exotic physical phenomena. In this presentation, we will discuss the engineered atomic scale reconstruction at twisted vdW interfaces using electron microscopy, optical spectroscopy, and electrical transport. We then will discuss emerging electronic and optoelectronic physics in the vdW interface between homojunctions.