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Who doesn’t love a brownie? It’s the ultimate comfort food—beloved around the world and even beyond it. Astronauts aboard the International Space Station have brownies on their menu too .

But what makes a perfect brownie? That depends on who you ask. Some like a light, cake-like crumb. Others want a dense, fudgy center or a chewy bite.

To tailor your brownies to your taste, you need to understand the science behind them. “Each ingredient has a specific role, and the ratios between them determine whether the brownie turns out fudgy, cakey, or chewy,” explains Dr. Lesa Tran , a chemistry professor at Rice University.

What each ingredient really does

Flour

Flour is the backbone of your brownie.…