In the 1980s, Clayton Christensen cofounded a startup that took over a market niche from DuPont and Alcoa. That experience left Christensen puzzled. How could a small company with few resources beat rich incumbents?It led to his theory of disruptive innovation, introduced in the pages of Harvard Business Review in 1995 and popularized two years later in The Innovators Dilemma. The idea has inspired a generation of entrepreneurs. It has reshaped R&D strategies at countless established firms. And it has changed how investors place billions of dollars and how governments spend billions more, aiming to kickstart new industries and spark economic growth.But disruption has taken on a popular meaning well beyond what Christensen’s research describes. Some critics argue that the theory lacks evidence. Others say it glosses over the social costs of lost jobs of bankrupted companies. And debate continues over the best way to apply the idea in practice.4 Business Ideas That Changed the World is a special series from HBR IdeaCast. Each week, an HBR editor talks to world-class scholars and experts on the most influential ideas of HBR’s first 100 years, such as shareholder value, scientific management, and emotional intelligence.Discussing disruptive innovation with HBR editor Amy Bernstein are: Rita McGrath, professor at Columbia Business School Felix Oberholzer-Gee, professor at Harvard Business School Derek van Bever, senior lecturer at Harvard Business SchoolFurther reading: HBR: What Is Disruptive Innovation?, by Clayton M. Christensen, Michael E. Raynor, and Rory McDonald New Yorker: The Disruption Machine: What the Gospel of Innovation Gets Wrong, by Jill Lepore Business History Review: How History Shaped the Innovator’s Dilemma, by Tom Nicholas HBR: Disruptive Technologies: Catching the Wave, by Joseph L. Bower and Clayton M. Christensen