Non-thermal plasma (NTP), often referred to as cold plasma, represents a highly efficient and innovative tool in chemical reaction engineering. It operates on the principle that electrons within the plasma are maintained at a significantly higher temperature than the bulk gas, facilitating chemical reactions under near-ambient temperatures and pressures. This technology is primarily utilized in research and laboratory environments to drive a wide array of gas-phase and liquid-phase chemical reactions, particularly in the realm of sustainable chemistry and advanced material synthesis. Key applications include the development of greenhouse gas (GHG)-free hydrocarbon reforming processes, the synthesis of fine chemicals, ammonia production, and the effective treatment of contaminated water. NTP systems are engineered to generate high-energy electrons and a variety of reactive species, such as radicals, ions, and excited molecules. These species possess the energy required to break strong chemical bonds and significantly enhance reaction kinetics, even for reactions that are thermodynamically unfavorable under conventional conditions. A diverse range of NTP sources are employed, including dielectric barrier discharge (DBD), pulsed discharge, microdischarge, radio frequency discharge, and glow discharge plasmas. These systems typically operate with low electrical power inputs, often in the range of a few hundred watts, where electron temperatures can reach up to 10,000 K while the neutral gas remains close to room temperature. This unique non-equilibrium state enables efficient chemical conversion with substantially lower energy consumption compared to high-temperature thermal plasma processes. Moreover, NTP reactors can be designed to be compact and lightweight, making them suitable for portable and distributed applications. Non-thermal plasma is extensively applied in hydrocarbon reforming to produce hydrogen-rich gas from various feedstocks, including gasoline, diesel, and methane. This offers a compelling alternative to traditional catalyst-based methods, which often suffer from issues like catalyst poisoning and high operational costs. It stands as a promising technology for converting natural gas into valuable fuels and chemicals under mild conditions, with significant potential for integration into distributed processes powered by renewable energy sources. In the field of material synthesis, NTP, particularly through plasma-liquid interactions, is utilized for the rapid fabrication of nanostructures and nanoparticles, including noble metal colloids. Further applications encompass ammonia synthesis, carbon dioxide (CO2) reduction, and the degradation of volatile organic compounds (VOCs). The ability of NTP to operate at lower temperatures also minimizes electrode erosion and allows for the processing of temperature-sensitive materials. NTP systems can be synergistically integrated with catalysts in plasma-catalysis configurations to further boost chemical conversion rates and enhance product selectivity. The chemical outcomes of the process can be precisely controlled by adjusting various plasma parameters, such as power input, gas composition, and electrode geometries. To gain a deeper understanding and optimize the underlying plasma chemistry, advanced diagnostic tools like optical emission spectroscopy (OES), in-situ Fourier-transform infrared (FTIR) spectroscopy, and tunable diode laser absorption spectroscopy (TDLAS) are frequently employed. Furthermore, plasma-liquid interaction systems offer the unique capability to generate reactive species directly within liquids or at the gas-liquid interface, opening novel chemical pathways for synthesis and environmental applications, including advanced water treatment.