Marc Andreessen and Ben Horowitz
trailblazers 2013 andreessen horowitz
Andreessen (left) and Horowitz

Andreessen Horowitz
Founded: 2009

Watch: The keys to Andreessen Horowitz's success

Andreessen, 41, and Horowitz, 46, are making waves in Silicon Valley not just for their investments (they've backed Facebook (FB), Skype, and Instagram, among others) but also for the institutional support they provide their portfolio companies. The firm's staff of 66 offers unlimited assistance in design, marketing, hiring, and more. Andreessen Horowitz has seven general partners, all of them former entrepreneurs; the goal was to create a venture capital firm that the founders would have sought out during their own startup days some 20 years ago. Andreessen co-founded Netscape in 1994, and Andreessen and Horowitz in 1999 co-founded software company Opsware, which Hewlett-Packard (HPQ, Fortune 500) acquired in 2007 for $1.6 billion. Entrepreneurs are also drawn to Andreessen and Horowitz themselves. (The firm doesn't have a CEO; the co-founders share management duties.) Horowitz is one of tech's most sought-after CEO mentors, and the superconnected Andreessen sits on the boards of eBay (EBAY, Fortune 500) and HP.

  @FortuneMagazine - Last updated February 08 2013 12:28 PM ET
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