To caramelize means to cook sugar (or foods containing sugar) until it turns brown and develops a rich, sweet flavor. When you heat sugar slowly, it melts, then transforms from clear to golden to deep brown, becoming thick and sticky with a taste that's both sweet and slightly bitter, more complex than plain sugar.

Cooks caramelize onions by cooking them slowly in a pan until their natural sugars turn golden brown and deliciously sweet. You might see caramelized sugar on top of a crème brûlée, forming that crispy layer you crack with your spoon. Bananas Foster, a famous dessert, features bananas caramelized in butter and sugar.

The process requires patience and attention. If you heat sugar too quickly or too long, it burns and tastes bitter. But done right, caramelization creates flavors you can't get any other way. Home cooks caramelize everything from apples to Brussels sprouts, transforming ordinary ingredients into something special through heat, time, and chemistry.