The core DNA of Lean Startup is a beautiful helix. The two loops of this helix focus on two ideas that lie at the heart of the Lean methodology--agile development and customer development. Tied together, these two approaches enable developers to create products that are truly user-driven.
The outer loop of the helix involves working with the market to discover customer needs and the context in which they emerge, and to test whether possible solutions meet these needs. Originally coined by Steve Blank, this loop is known as customer development.
The inner loop involves a rapid iterative software development cycle of understanding needs identified by customer development and developing solutions that meet these needs:

Agile development has matured over the last decade, and Scrum and XP are common today in many organizations. Agile radically...