  Moire superlattices-twisted van der Waals (vdW) structures with small
angles-are attracting increasing attention in condensed matter physics, due to
important phenomena revealed therein, including unconventional
superconductivity, correlated insulating states, and ferromagnetism. Moire
superlattices are typically comprised of atomic layers of vdW materials where
the exotic physics arises from the quantum electronic coupling between adjacent
atomic layers. Recently, moire electronics has motivated their photonic
counterparts. In addition to vdW materials, twisted photonic systems can also
be comprised of metamaterials, metasurfaces, and photonic crystals, mediated by
interlayer electromagnetic coupling instead. The interplay between short-ranged
interlayer quantum and long-ranged electromagnetic coupling in twisted
structures are expected to yield rich phenomena in nano-optics. This
perspective reviews recent progress in twisted structures for nanophotonics and
outlooks emerging topics, opportunities, fundamental challenges, and potential
applications.
