Tom Ryan still remembers when he was hired by Pizza Hut in 1988 to be its director of new products. Shortly after he started there, he told First We Feast he vividly remembers his company's chief operating officer walking into his office and delivering a warning that stuck with him: “You're in trouble, because everything there is to do with pizza has now been done.”

“I went home that night and said, you know, this is how a lot of the world thinks about things,” Ryan told?The Denver Post in 2013. “I don't think like that. I'm gonna change the world.”

He did. Ryan, who holds a doctorate in flavor and fragrance chemistry from Michigan State University, went on to create some of the most successful fast-food innovations of the past three decades. His portfolio includes Pizza Hut's stuffed crust pizza as well as the McDonald's Dollar Menu, the McGriddle, and the McFlurry, plus Smashburger, the burger chain he co-founded in 2007 and sold to Jollibee in 2018.

The science of stuffed crust

Ryan's stuffed crust breakthrough at Pizza Hut came after he found “cheese is the most important thing that drives most people's value perception of pizza.” But engineering cheese inside the crust presented a technical challenge. His first attempt, he recalled, tasted pretty good, but looked like a tire.

“The real work came after we realized it was [good] idea, and we had to figure out how to fit [the cooking process] into our operation,” Ryan told First We Feast. “Baking a pizza with cheese in the crust and baking a thin pizza is like baking a turkey and a chicken wing at the same time. And so there was a lot of technical work that went into how you design the dough and the pan it's cooked in, so that you can have the [two elements of this] product coming through the same oven in the same amount of time.”

After a year and a half of development work, the product launched in 1995. Pizza Hut sold more than $1 billion worth of stuffed crust pizzas in the first year, and overall sales rose approximately 10%.

Ryan also introduced the Meat Lover's and Pepperoni Lover's pizzas, breadsticks, chicken wings, and Sicilian pizza during his tenure at Pizza Hut.

Moving to Mickey D's

McDonald's recruited Ryan in the late 1990s as Worldwide Chief Concept Officer. Tasked with boosting breakfast sales, he created the McGriddle---“We basically took the Grand Slam Denny's breakfast and put it in your hand,” as he described it to First We Feast.

The innovation required solving how to deliver maple flavor without mess. “We worked hard to get those little syrup crystals, and once we had that, McGriddles happened really quickly,” Ryan said.

He also developed McDonald's fruit-and-yogurt parfait using vanilla yogurt that “tasted more like vanilla pudding” to appeal to Americans who didn't actually like yogurt. In addition, Ryan introduced the McFlurry to U.S. markets and spearheaded the Dollar Menu, which launched nationally in late 2002.

Spreading the culinary wealth

After positions at Quiznos---where he created the Steakhouse Beef Dip and Prime Rib Sub---Ryan co-founded Smashburger with Rick Schaden in 2007. The chain grew to more than 360 locations and was twice named by?Forbesas “America's Most Promising Company.”

Then Jollibee came along. The Philippines-based company acquired Smashburger in stages---first buying a 40% stake for $100 million in 2015, then 85% in another $100 million deal in 2018, before finally getting 100% of the company in a $10 million deal just 10 months later---for a total investment north of $445 million.

Gourmet Magazine?named Ryan one of the “25 Top Food Entrepreneurs of the Last 25 Years.” He remains CEO of Smashburger and serves as Global Taste Advisor to Jollibee, while also founding Tom's Urban and Tom's Watch Bar (Tom's Watch Bar餐飲品牌).

For this story, Fortune used generative AI to help with an initial draft. An editor verified the accuracy of the information before publishing.