Microwave ovens work by moving food particles against each other on a molecular level, using the food's water molecules. Foods with a high moisture content tend to cook more successfully in microwaves for this reason, leaving lower water-content foods more prone to drying out during cooking. Meat, eggs and cheese have a tendency to toughen in the microwave, unless cooked on lower power settings. Additionally, large items will overcook on the outside before cooking through to the middle unless power settings are carefully reduced.