**1. Introduction**

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We are pleased to introduce to you this Special Issue of *Nanomaterials* on 'Luminescence Nanomaterials and Applications'. Luminescence is a phenomenon that we experience daily in our work and lives. Emerging nanotechnology and quantum dots offer a new class of materials to make our lives better. For example, the applications of luminescent nanoparticles for medical research are taking advantage of their high quantum yield, multi-colors, high photostability, large surface-to-volume ratio, surface functionality, and small size. For solid-state displays, they can provide more colors by simply adjusting the size of the particles. In this Special Issue, we discuss nanomaterials with quantum size confinement, photoluminescence, upconversion, thermoluminescence, and long persistence, as well as their potential applications in cell labeling, imaging, detection, and sensing. This Special Issue also covers the synthesis of luminescence nanomaterials, applications for in vitro and in vivo imaging, detection based on fluorescence resonance energy, and the applications of luminescent nanoparticles for photodynamic activation and solid-state displays, as well as new materials and structures, such as perovskite quantum dots, and novel phenomena, such as aggregation-induced emissions. In total, we have 15 papers (2 reviews and 13 research articles) for this Special Issue, which are summarized below:
