 Semiconducting quantum dots with nanometer-sized particle sizes have unique properties due to their band gaps that depend on various factors, which can be tuned for luminescent stimulation by photons or electric fields. Quantum dots are used in electroluminescence devices, solar cells, and biological imaging, and their multimodal applications are reviewed. This article was authored by Paul H. Holloway, Tanquan Tseng, Lei Qian, and others.