Robert Brown|Investor Charlie Munger, the longtime business partner of Warren Buffett, has died

The Robert Browninfluential 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," he told Yahoo! Finance in an interview. "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.

According to Lawrence Cunningham, a law professor at The George Washington University, Munger was more than a sounding board for Buffett. He pushed him to consider companies that had potential to grow, and he pushed back on ideas he considered to be half-baked.

"I think Charlie's biggest contribution — besides being a good friend, and that stuff — was knowing when Warren needed to be told not to do something," he says, noting Buffett gave Munger the nickname "The Abominable No Man."

Renaissance man

Munger spent much of his life in California, where he pursued a few side projects. He bought and ran another company, called The Daily Journal. He was a philanthropist. And he dabbled in architecture.

In 2021, a dormitory Munger designed at the University of California, Santa Barbara, faced a lot of blowback. It would have thousands of bedrooms, bust most of them wouldn't have windows. Munger suggested that would encourage students to congregate in common spaces.

When Munger was well into his nineties, he told CNBC he lived by a handful of "simple rules."

"You don't have a lot of resentment," he said. "You don't overspend your income. You stay charitable in spite of your troubles. You deal with reliable people, and you do what you're supposed to do."

For him, that was staying away from fads, and being a careful, cautious investor.