Lean methods have been used for over 50 years in production processes, producing huge economic benefits. They are based on many principles that are transferable to product development. In fact, these methods are the only practical way to simultaneously achieve large improvements in the speed, quality, and cost of product development. However, using lean methods in product development requires some insight. Certain methods that work in Lean Manufacturing are toxic in a product development environment. For example, if we try to eliminate all variability we will, as an unfortunate side effect, eliminate all innovation.