Microwaves do not inherently cool down by themselves. When a microwave oven is running, it emits electromagnetic waves (microwaves) that excite the water molecules within the food you're heating. This molecular excitation generates heat, which, in turn, cooks or heats up the food.
Once you turn off the microwave, the emission of microwaves stops, and the heat generation ceases. However, the food inside the microwave will continue to retain the heat it has absorbed during the cooking process. The rate at which the food cools down depends on various factors, including the initial temperature, the type of food, its mass, and the surrounding environment's temperature.
The cooling process in a microwave can be compared to letting hot food cool down on a kitchen counter. The heat gradually dissipates into the surrounding air, and the food's temperature decreases over time. It's essential to be cautious when handling hot food from a microwave, as it can still cause burns even after the microwave has been turned off.
Remember to use oven mitts or other appropriate tools to handle hot containers, and allow the food to cool to a safe eating temperature before consuming.