Reginald Browne tilts his 6-foot-5-inch frame forward to reach a chirping phone.

“What do you want, what do you need?” he asks.

It’s his standard greeting for just about anyone who calls, Bloomberg Markets magazine will report in its April 2014 issue. This time, it’s a representative of a large public pension fund who’s thinking about moving money into exchange-traded funds for the first time. Browne launches into his education mode, patiently answering questions on how closely an ETF will really track its index, how quickly the investor can get in and out and how much it will cost to trade.

Behind Browne, in a cramped midtown Manhattan office, the traders who work for him offer a marked contrast to his easy calm. In two back-to-back rows, they fire questions and instructions at each other as they watch banks of flickering computer monitors and make decisions in seconds on the prices at which they will buy and sell ETFs.

“What are we offering for EEM?” demands one.

That’s the iShares MSCI Emerging Markets ETF, a $31 billion collection of stocks from more than 20 countries. Browne, 45, known as Reggie, is a senior managing director and head of ETF trading at New York–based Cantor Fitzgerald LP. There, he presides over one of the most complicated market-making operations on Wall Street. ETFs are among the fastest-growing investment classes in the history of finance -- with $2.4 trillion in assets under management as of the end of December, a number that has doubled in just the past four years.

A Key Force

Browne, who until September was head of ETF trading at Knight Capital Group Inc. (now KCG Holdings Inc.), has helped create hundreds of funds -- advising providers such as BlackRock Inc.’s iShares, Charles Schwab Corp. and Vanguard Group Inc. He has also been a central figure in helping ETFs grow globally and a key force in selling their merits to investors.

“Reggie’s one of the most influential people in building the ETF landscape over the last decade,” says Rodney Comegys, global head of capital markets at Vanguard, the third-largest provider of ETFs. “He’s a missionary, especially in the institutional space. He’s the person on the edge showing people the power of the exchange-traded fund.”

The son of a U.S. Air Force loadmaster and a banker, Browne downplays the credit ETF providers give him.