A chemical reactor and method of using the same. The reactor comprises first and second micro-engineered discrete flow passages for receiving chemical fluids. The first fluid passage receives a first chemical fluid in which a chemical change or reaction in the fluid can be initiated by subjecting the fluid to a stimulus. A stimulation means is located in, or adjacent to, the first flow passage, and is operable to stimulate a chemical change or reaction in the first fluid. The second micro-engineered discrete flow passage receives a second chemical fluid which will interact with the stimulated first fluid when contacted by the stimulated first fluid. The first and second flow passages converge at a first region to form an outlet passage within which the first and second fluids may contact each other.