Two-dimensional (2D) van der Waals (vdW) heterostructures provide an unprecedented opportunity in designing new material systems because the lack of dangling bonds on the surfaces of vdW materials enables the creation of high-quality heterointerfaces without the constraint of atomically precise commensurability. The ability to build artificial heterostructures, combined with the recent advent of various 2D materials such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), enables not only the fundamental investigation of quantum phenomena in low dimensional systems but also their applications for novel electronic and optoelectronic devices. In addition, organic materials that can be epitaxially assembled on the vdW surfaces of 2D materials may offer another degree of freedom to create intriguing quantum heterostructures. In this presentation, I will mainly discuss two interesting heterostructures based on inorganic/organic vdW systems: (1) atomically thin p-n heterojunctions fabricated by the vdW assembly of semiconducting TMDC monolayers and (2) epitaxial heterostructures between the organic rubrene crystal and h-BN dielectric layers. We investigated the charge transport and optoelectronic properties in these vdW heterostructures, and found the unique characteristics compared with conventional material systems.