 nanotechnology has been increasingly applied to improve oil recovery from depleted reservoirs. Nanoparticles can be used to reduce the viscosity of injected fluids, prevent asphaltine precipitation, increase the mobility of hydrocarbons, and decrease the interfacial tension between the fluid and the reservoir rock. Additionally, nanoparticle-based tar methods have been developed to target existing thermal, chemical and gas methods. These include nanofluidic systems, nanoemulsion flooding, and nanocatalytic processes. Despite the promise of nanotechnology in improving oil recovery, there remain several challenges and opportunities for future research. This article was authored by Xiaofei Sun, Yin Yuxiang, Guangping Chen, and others.