The innovators who shake up industries the most do so by reimagining how things should look from the ground up. Apple co-founder Steve Jobs imagined a world where everyone owned a computer, not just the corporations that could afford an IBM mainframe. Twitter cofounder Evan Williams imagined a world where everyone could publish content on the Internet, not just the media companies who could afford expensive Web publishing programs. Incremental innovations occur everywhere, but breakthrough innovations—the kind that leverage new technologies and business models to drive down costs, increase accessibility, and improve services—have tended to remain the province of the private sector. Return-seeking investors and entrepreneurs reap the financial rewards of changing the world by tearing down the structures of old industries.