2. Mark Zuckerberg
The social media giant isn’t adding users as fast as it used to, but it’s finally minting money from them. Revenue and profits keep trouncing estimates—and the company proved its critics wrong when it comes to mobile monetization: in the second quarter this year, mobile advertising accounted for almost two-thirds of ad revenue, while the number of users checking in on mobile devices grew to 650 million.David Ramos—Getty Images
Fortune’s 40 Under 40 is an annual list celebrating the young superstars rocking the business world across sectors from travel to energy to social media. This year’s 40 Under 40 was announced Thursday morning, and it’s jam-packed with young notables from Uber CEO Travis Kalanick to Yahoo boss Marissa Mayer.
Scroll through some of Fortune’s 40 Under 40 above. For the full list, visit Fortune.com.
1. Travis Kalanick & Brian Chesky
They’re revolutionizing two very different industries, but this was the year that Kalanick and Chesky became the figureheads for the ongoing clash between the great potential of the Internet economy and the rules and regulations of the old economy. Charles Eshelman—Getty Images for AOL2. Mark Zuckerberg
The social media giant isn’t adding users as fast as it used to, but it’s finally minting money from them. Revenue and profits keep trouncing estimates—and the company proved its critics wrong when it comes to mobile monetization: in the second quarter this year, mobile advertising accounted for almost two-thirds of ad revenue, while the number of users checking in on mobile devices grew to 650 million. David Ramos—Getty Images3. Matteo Renzi
The youngest Prime Minister in Italian history came into office in February on a burst of promise. A charismatic outsider, he pledged to break his center-left Democratic Party’s long ties to labor while he chased renewal by challenging Europe’s zeal for austerity.Andrew Cowie—AFP/Getty Images4. Andriy Kobolyev
Kobolyev has his hands full—and not just because at just 36, he runs a company that employs 175,000 and accounts for one-eighth of his country’s GDP. He took the reins at Ukraine’s state-owned oil and gas company in March, a week after his predecessor was arrested on corruption charges and in the midst of his country’s bitter conflict with Russia, which also is Ukraine’s main gas supplier. Vincent Mundy—Bloomberg/Getty Images5. Jan Koum
The Ukrainian-born engineer toiled at Yahoo for nearly a decade with co-founder Brian Acton before traveling South America and eventually developing WhatsApp, the simple, free mobile app that works a lot like traditional text, letting users send and receive calls, video, and pictures, as well as messages.Albert Gea—Reuters6. Marissa Mayer
No one ever said turning around Yahoo would be easy, Mayer is facing restless investors as ad revenue remains challenged—and in the wake of the sale of part of the company’s stake in Chinese e-commerce giant Alibaba.Mario Tama—Getty Images7. Tom Farley
When he was just 30, Farley, was named the head of the New York Board of Trade. It was a tough gig: The NYBOT was an also-ran commodities exchange that did most trading on its physical floor at a time when the rest of Wall Street was going electronic—and being young and coming from the tech world won Farley immediate enemies with its old-school traders.Richard Drew—AP8. Kevin Systrom
Snap-happy Systrom has just begun to make good on Mark Zuckerberg’s $1 billion bet on the company in 2012, rolling out sponsored ads for the first time in November 2013. Since the acquisition—which paved the way for Facebook’s fatter bids for upstarts like WhatsApp ($19 billion), Oculus Rift ($2 billion), and SnapChat ($3 billion)—the mobile photo platform has ballooned about 10 times in both size and audience, now having more than 200 million active monthly users and some 150 employees.David Paul Morris—Bloomberg/Getty Images9. Elizabeth Holmes
Holmes, whom we put on our cover in June, dropped out of Stanford when she was 19 to found Theranos, a revolutionary blood analytics company. Ten years later her private, Palo Alto–based company employs more than 500 and is valued by investors at about $9 billion. (She retains more than half the stock; you do the math.)Steve Jennings—Getty Images for TechCrunch10. Jesse Cohn
Back when he was a teenage computer camp geek in the 1990s, Jesse Cohn taught himself to program and earned an advanced IT certification issued by a company called Novell. So when some 15 years later—as a portfolio manager at one of the most influential activist hedge funds—Cohn launched a hostile bid to acquire Novell, he mentioned the accolade in his letter to the board. Elliott Management
