The first person to truly integrate an entire production process was Henry Ford by lining up fabrication steps in process sequence, using standardized work and interchangeable parts, which he called Flow production (1913). The problem with Ford’s system was its inability to provide variety. The Model T was limited to one color (Black) and it was also limited to one specification so that all Model T chassis were essentially identical up through the end of production in 1926.
Kiichiro Toyoda, Taiichi Ohno, and others at Toyota looked at the Ford’s situation in the 1930s, and more intensely just after World War II (1950). While Ford produced 8000 vehicles per day, Toyota had produced 2500 vehicles in 13 years. Toyota wanted to scale up production but faced a lack of financial resources for the huge number of inventory and sub assemblies they saw at the Ford’s plant. It occurred to them that a series of simple innovations might make it more possible to provide both continuity in process flow and a wide variety in product offerings. Toyota developed the Toyota Production System (TPS). TPS borrowed Fords ideas but since they couldn’t afford the huge inventories Toyota introduced its Just in Time (JIT) philosophy and the ‘Pull Concept’.
A detailed description of the Toyota Production System and its 14 principles are described in the book ‘The Toyota Way’, (2004) [Jeffrey K. Liker, PhD], . The thought process of Lean was thoroughly described in the book ‘The Machine That Changed the World ‘(1990)  and in a subsequent volume, ‘Lean Thinking’ (1996), [James P. Womack and Daniel T. Jones],  in which the described the five Lean principles.
|1. Customer Value
||Specify the value desired by the customer
|2. Waste elimination
||Identifying and eliminating non-value added activities
|3. Continuous flow
||Make the product flow continuously
|4. Pull instead of Push
||Using pull between steps where continuous flow is possible
|5. Continuous Improvement
||Manage toward perfection
Toyota became in 2008 the world’s largest Automaker in terms of overall sales. This continued success has over the past two decades created an enormous demand for greater knowledge about Lean thinking. There are literally hundreds of books and papers and numerous other resources available to this growing audience.