Van der Waals heterostructures are stacks of thin (down to monolayer) layered materials assembled mechanically, exhibiting fundamentally new optical, transport, magnetic, and superconducting properties. These structures cannot form naturally or be grown synthetically. In our group, we assemble such heterostructures and investigate their unique properties, aiming to create prototypes for future microelectronic devices, electrically controlled superconductivity, radiation detectors and emitters, and to study new interfacial phenomena. Working with two-dimensional and layered materials, we discovered that they possess a wealth of unexplored optical properties. Another class of materials we study is topological insulators—a type of narrow-gap semiconductor with surface states protected from scattering due to band inversion. The non-local nature of these states and the spin-momentum coupling in them have attracted significant attention. Working with small-scale objects has required us to develop new tools, including custom-designed microscopes, lithography systems, and novel fabrication processes, which has opened up a vast area for innovation and discovery.