The influential investor Charlie Munger, longtime vice chairman of the conglomerate Berkshire Hathaway, has died. He was 99 years old.

With Warren Buffett, Munger built Berkshire Hathaway into a multi-billion dollar behemoth.

“They complemented each other in their approach to investments in a very nice way,” says David Kass, a finance professor at the University of Maryland.

Munger was a “value investor,” who liked to buy stocks when a company’s share price was low relative to its fundamental value. But he also believed in the power of trusted brands — and in valuing growth.

Over the years, Berkshire Hathaway made large investments in dozens of household names, including Kraft Heinz, Bank of America, and Coca-Cola. Its portfolio included car companies, grocery stores, and insurers.

“Berkshire Hathaway could not have been built to its present status without Charlie’s inspiration, wisdom and participation,” Buffett said, in a statement.

For Munger, simplicity was a guiding principle.

“I can’t think of a single example in my whole life where keeping it simple has worked against us, “We’ve made mistakes, but they weren’t because we kept it simple.”

Munger grew up in Omaha, Neb., not far from Buffett’s childhood home. According to Kass, a local physician introduced them to each other, and “they hit it off immediately.”

After serving in the U.S. Army, Munger attended Harvard Law School, and he went on to found Munger, Tolles & Olson, a law firm headquartered in Los Angeles.

Today, Buffett may be better known, but Kass says Munger played a big role in what was a really unique business partnership.

“The Abominable No Man”

Munger was a straight shooter, with a dry sense of humor, and Berkshire Hathaway shareholders saw his personality on display at the company’s annual meetings in Omaha, where he and Buffett fielded questions for hours on end.

Often, Buffett answered questions at length. Then, Munger chimed in with something pithy or a perfect one-liner. The audience roared.