Though there is only one way for a given material to be defect-free, there are many possibilities for materials to be imperfect. The presence of defects imparts the host material with new micro/quantum states or energy configurations that can strongly influence many physical properties such as the electronic structure, magnetic properties, and thermal conductivity. Indeed, when distributed appropriately in the low-dimensional host materials, defects could result in exotic quantum states of matter, which have distinct physical characteristics (e.g. electronic states in nano-superconductors or topological insulators) compared to other prevalent states. For instance, carbon chemistry at the nanoscale exemplifies such defect-induced phenomena and continues to surprise us through the most recently discovered forms of carbon (e.g., carbynes and Q-carbon) and their potential applications. Additional topics include fundamental physics and applications of defects and dopants in topological insulators and materials relevant for energy generation and storage. This symposium will focus on microscopic and spectroscopic studies of defect phenomena and new states of matter at the nanoscale. Recent developments in defect science and engineering suggest that defects govern the properties of nanostructures to the same or even to a greater extent as they do in bulk solids, leading to a new perspective in which defects in materials are viewed. However, efforts in delineating defect-induced phenomena are at best scattered. It is imperative now to focus on common platforms, such as the one provided by this symposium, to collectively understand the fundamental behavior of defects in materials, and learn new ways to suitably engineer them for desired applications in catalysis, energy, and information technology.