36. John Hering & Salman Khan (Tie)
40u40 main sal khan john hering
Khan (left) and Hering (right)

John Hering
Age: 29
Co-founder and CEO, Lookout

The same wide-eyed University of Southern California student who hacked a Bluetooth network from a record-setting distance of over a mile away and scanned celebrities' phones on the red carpet of the 2005 Academy Awards has turned his free mobile security application, Lookout, into one of the most downloaded apps on the Android. (It released for iOS platforms in 2011.) Lookout uses its algorithm-based Mobile Threat Network to scan your smartphone for Malware and other unwanted intrusions. A serial entrepreneur, Hering was able to raise $75 million to fuel his San Francisco--based startup's rapid growth. In 18 months Lookout has tripled in size, largely through deals with major telecom providers like Sprint, T-Mobile, and Verizon. It now has more than 25 million users and is valued at $1 billion.

Fave hobby: Umm ... hacking.

--Eli Epstein

Salman Khan
Age: 36
Founder and executive director, Khan Academy

Khan's web-based tutorials have led many to rethink the way kids learn. Inspired by the nonprofit's meteoric growth, traditional universities like Harvard and MIT have begun experimenting with offering free online courses of their own. The four-year-old nonprofit Khan Academy, which offers courses spanning trigonometry to art history and has attracted donations from the likes of John Doerr and the Bill & Melinda Gates Foundation, now draws over 5 million visitors a month; its YouTube channel has over 180 million views, and counting. And Khan's first book, in which he lays out his vision for online universal education, hits shelves this month.

School rules: Khan has four degrees - three from MIT and an MBA from Harvard.

--M.L.


  @FortuneMagazine - Last updated October 17 2012 05:11 PM ET
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