 Graphitic carbon nitride, G, C3N4, a two-dimensional conjugated polymer, has gained broad interdisciplinary attention as a low-cost, metal-free, visible light-responsive photo catalyst for environmental remediation due to its excellent electronic band structures, electron-rich properties, basic surface functionalities, high-physical chemical stabilities and earth abundance. Recent research has focused on designing and constructing G, C3N4-based materials for catalysis, sensing, imaging, and white-light emitting diodes, with potential future developments in emerging properties and applications. This article was authored by Iwo Wang, Chen Dong-Wang, Li Fu, and others.