Here’s why the first-generation immigrants say the key to achieving the American dream is giving back.

When Peggy Cherng moved to the United States from Hong Kong in 1967 to attend Baker University, she didn’t do it with the intention of becoming a billionaire — but that’s exactly what happened.

An electrical engineer who once coded battlefield simulators for the US Navy, Cherng and her husband Andrew opened the first Panda Express in a Los Angeles-area mall in 1983, serving Chinese food favorites cafeteria-style. Cherng used her engineering PhD to help streamline the restaurant’s logistics by using technology to track inventory and reorder ingredients long before the practice was widespread.

The brand has since grown to over 2,000 locations and built a $3 billion fortune for the Cherngs in the process. Cherng and her husband are now the co-CEOs of fast-casual Chinese food empire Panda Restaurant Group (PRG), the parent company of Panda Express.

But technology isn’t Peggy Cherng’s only major addition to Panda Express. Next to the cash register at each location, there is a small box labeled “Panda Cares,” where diners and staffers alike are encouraged to donate to the company’s charitable arm. In an exclusive conversation with Business Insider, Cherng credited a lot of Panda Restaurant Group’s success to that box and the company’s overall emphasis on giving back.

Read the full interview on Business Insider.