This session focuses on the fundamental physics and exotic applications in photonic/acoustic micro-/nano-structures and topological meta-crystals, including numerical calculations and experimental results, leading to the new phenomena of photonic/acoustic crystals, photonic/acoustic meta-crystals, metamaterials and metasurfaces. Example topics include bound states in the continuum in micro-/nano-structures, topological effects in classical systems, abnormal reflection/transmission/absorption in metasurfaces, bandgap engineering in photonic/phononic crystals, nonlinear optics in photonic/plasmonic meta-crystals, and novel optical devices, etc.