Red-light has been used as phototherapy in the medical field because of its long wavelength (620-750 nm) that can easily penetrate through the body of patients. Red-light can also be used for many commercial, industrial, and medical applications, as well as a necessary device source of red laser eyesight for military weapons. Thus, photoluminescence (PL) and electrolu- minescence materials and electronic devices, with the capability to emit red-light under proper conditions, have been a long- time scientific pursuit after the first successful red-light light- emitting-diode (LED) was obtained in the early 1960s. Nano/ microstructured semiconducting materials are considered as the primary sources for enhancing red-light emitting efficiency and enhancing the precision of laser-guided weapons. In addition, red-light emitting nano/microstructured materials may be used as red fluorescence powder, acting as one of the basic fluorescence additives for preparing white LED fluorescent lamps. Indium oxide (In2O3), a promising wide bandgap semiconductor with a bandgap of 3.6 eV, shows technologically important applications in optoelectronic devices such as lasers, fluorescent lamps, orientation lamps, display devices, and infrared reflectors. For example, it has been reported that nanosized In2O3materials exhibit tunability in the wavelength ranges from ultraviolet (UV) to visible blue-green as well as yellow emission for optoelectronic devices. However, red- light emission was rarely reported from these In2O3 nanostructures. Wenyan Yin and his team report that interstitially N-doped In2O3 nano/ microstructures including nanorods, nanoellipses, microspheres, and microbricks, which have recently been developed in their group by annealing the corresponding In(OH)3 precursors, show a unique and wide range red-light emission under 350 nm wavelength excitation, in addition to blue-light emissions. They first made the arrays of In2O3 and then they doped it with N, filling interstitial vacancies in the crystal cells.