To preheat is to bring an oven, grill, pan, or dish up to the required temperature before food goes in. The step is essential for baking, where doughs and batters need immediate heat to set structure, activate leavening, and develop crust before they spread or collapse; a cold oven produces pale, dense results. Roasting and grilling similarly depend on preheated surfaces for proper searing and browning. Most domestic ovens need 10 to 15 minutes, and an oven thermometer reveals that many run hot or cold versus the dial setting. Preheating baking stones or heavy trays stores thermal mass for crisp bases. The energy cost of preheating is real but necessary; skipping it to save power is a false economy that ruins food. Professional kitchens preheat as a matter of mise en place discipline.