He’s not a household name like Gates, Jobs, or Zuckerberg. His face isn’t known to millions. But during his remarkable 20-year career, no one has done more than Marc Andreessen to change the way we communicate. At 22, he invented Mosaic, the first graphical web browser—an innovation that is perhaps more responsible than any other for popularizing the Internet and bringing it into hundreds of millions of homes. He cofounded Netscape and took it public in a massive (for that time) stock offering that helped catalyze the dotcom boom. He started Loudcloud, a visionary service to bring cloud computing to business clients. And more recently, as a venture capitalist, he has backed an astonishing array of web 2.0 companies, from Twitter to Skype to Groupon to Instagram to Airbnb.