You can't. The unopened chestnuts can't be heated directly in the microwave oven, because the inside of chestnuts is a closed space. When heated, the temperature and moisture in the chestnuts will be too high, causing an explosion. If you need to heat chestnut, you can cut a hole before heating, and be careful not to open it too big. Don't heat it in the microwave for too long after cutting, or it will explode easily. It is best to cut a small gap with scissors without shell, so that the water can flow out quickly and the pot will not explode when heated. The principle of microwave heating is to make the food molecules vibrate and warm up gradually through their own heat, so the heating time should not be too long to avoid hard taste or other adverse effects.