The technique was originally developed by Sakichi Toyoda and was used within the Toyota Motor Corporation during the evolution of its manufacturing methodologies. It is a critical component of problem-solving training, delivered as part of the induction into the Toyota Production System . The architect of the Toyota Production System, Taiichi Ohno , described the 5 Whys method as "the basis of Toyota's scientific approach . . by repeating why five times, the nature of the problem as well as its solution becomes clear."  The tool has seen widespread use beyond Toyota, and is now used within Kaizen , lean manufacturing , and Six Sigma .