We all know pizza tastes delicious. If someone says otherwise, we might wonder if they’ve suffered some kind of traumatic injury to their taste buds. But what’s the secret behind pizza’s sexy, flavor-packed appeal?

From a scientific perspective, prehistoric humans probably would have loved pizza, too, if it had been invented at the time. “We are naturally drawn to foods high in fat and sugar because of the nourishment we received from such foods during our evolution in resource-poor environments,” one study has noted. “However, we are also drawn to foods with complex layers of balanced flavors composed through the art and science of cooking.”

In a recent article for The Conversation, Jeffrey Miller, an associate professor of hospitality management at Colorado State University, summed up pizza’s appeal: “Humans are drawn to foods that are fatty and sweet and rich and complex,” he wrote. “Pizza has all of these components. Cheese is fatty, meat toppings tend to be rich, and the sauce is sweet.”

Related: Why pizza is the feel-good food that’s good for you

Many pizza toppings, like tomatoes, cheese, pepperoni and pork, contain a compound called glutamate, Miller noted. “When glutamate hits our tongues, it tells our brains to get excited—and to crave more of it. This compound actually causes our mouths to water in anticipation of the next bite.”

Also found in beef, chicken and fish, glutamate stimulates the brain’s perception of umami flavor, which is both mysterious and highly desirable in any dish.

The beauty of pizza is that it’s stuffed full of glutamate due to the diversity of toppings, ingredient pairings and flavor combinations. “Tomatoes and aged cheese, the two foods that serve as the foundation of pizza, are also two foods packed with glutamates,” this nutritionist/blogger writes. The same goes for pizza sauce. “A typical slice of pizza may have about three tablespoons of tomato sauce providing 140 milligrams of glutamate. A tablespoon of Parmesan cheese that could be used to season the slice can provide about 75 milligrams of glutamate. Right when we take that first bite of warm pizza crust topped with tomato sauce and cheese, our taste buds are stimulated by glutamate, and so we’re hooked, and we want more.”

Add some sliced mushrooms, and you’ve got a smorgasbord of glutamates in a single serving.

Miller also points to two other factors that make pizza the perfect food, taste-wise:

Caramelization: This process occurs “when the sugars in a food become brown,” Miller says. “Most foods contain at least some sugar; once foods are between 230° and 320°, their sugars begin to turn brown….On a pizza, ingredients like onions and tomatoes become caramelized during baking, making them rich and sweet and flavorful. That brown and crispy crust is also the result of the dough caramelizing.”

The Maillard Reaction: Although it’s sometimes confused with caramelization, the Maillard reaction is a different process involving both sugars and proteins. “The Maillard reaction occurs when the amino acids in high-protein foods like cheese and pepperoni react with the sugars in those foods when heated,” Miller writes. “Pepperonis that become crispy with curled edges and cheese that browns and bubbles are examples of the Maillard reaction at work.”

Even leftover pizza still tastes amazing, in part because the pizza maintain its original structure while chilling, and the tomato sauce keeps the cheese fats from seeping into the dough and making it soggy. Meanwhile, the various flavors in the pie have had time to merge further and mellow in the fridge.

As Dr. Emma Davies, a science writer and editor with a PhD in food chemistry, has explained, “Pizza temperature affects taste perception, with cold foods generally having less intense flavors than warm ones. At temperatures between 15° and 35°C, heat-sensitive channels in the tongue’s sweet and bitter taste receptors open wide, setting off a chain reaction to send strong signals to the brain. At lower temperatures, the channels barely open, and the signals are weaker. Salty and sour taste receptors are not affected by temperature in the same way, and cold pizza can actually taste saltier and very, very tasty.”

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