In-rich InGaN/GaN nanostructures such as quantum wells (QWs) and quantum dots (QDs) were successfully grown by metal-organic chemical vapor deposition and their optical properties were investigated. Introduction of a relatively high growth temperature made it possible to grow In-rich InGaN/GaN QWs and growth interruption (GI) was effectively used to control their structural and optical properties. From In-rich InGaN/GaN QW structures grown without GI, enhanced thermal stability appeared in optical properties and thickness fluctuation in In-rich InGaN QWs could give intrinsic QD-like carrier localization centers. To enhance thermal characteristics, artificial formation of In-rich TnGaN/GaN QDs was done at a relatively lower growth temperature than that of QWs. From In-rich InGaN/GaN QDs, we could obtain high efficiency ultraviolet emission at room temperature.