20. Marissa Mayer
Marissa Mayer
VP, Google
Age: 36
Industry: Technology

Mayer started at Google 12 years ago as the then-startup's first female engineer. Today that makes her an old-timer by Google standards. In addition to overseeing local and mapping products like Google Earth, Street View, Google Maps, and local search, Mayer spearheaded the company's recent Zagat acquisition. Mayer has also expanded her influence outside Google: She's an angel investor in startups like Minted, One Kings Lane, and Square; she also hosted Obama in her home for a 2010 political fundraiser.

Travel ritual: She prefers redeyes.

Last updated October 25 2011: 5:11 PM ET
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Ones to watch

In addition to Fortune's 40 Under 40 list, we're also keeping our eye on these 20 innovators, young guns from a wide range of industries and backgrounds.