How Microwaves Work
Microwaves are powered by a tube called a magnetron, which emits short radio waves and causes water molecules in foods to vibrate at a high frequency. The friction or vibration between the water molecules and other molecules in the food creates heat and cooks food. Microwaves do not cook food from the inside out, as is commonly thought. In fact, only the outer portion gets cooked by the microwaves; the residual heat then cooks the interior portion.
Choosing a Power Level
Cooking at a higher power level exposes foods to more microwave energy. Therefore, it's best not to cook foods with a low water content on high heat because they will dry out faster. Instead, cook moist items quickly at a high power level and drier items at a low power level for a longer period of time. Cook foods that fall somewhere in the middle at an appropriate medium level.
In general, foods intended to be microwaved undergo the same preparation procedures as other methods. Food-borne illnesses are still a concern, so you should avoid cross-contamination from foods like chicken as usual. Microwaved items don't always cook evenly, depending on how they are arranged, what power setting was used and the base temperature of the food. Check the temperature of meat in several places to ensure it has cooked enough throughout to kill any harmful bacteria.
While food cooked in microwaves is perfectly safe, utensils and containers may not be. Most plastic dishes and containers manufactured today are microwave safe, but older plastic may not be. Microwaving a nonmicrowavable container can cause toxins within the material to leach into food. Metal should never be microwaved, as it does not react to the waves in the same way as glass or plastic. In fact, microwaving metal can cause a fire and ruin your microwave. In addition, never use a microwave oven if the door fails to securely close or its latches appear defective.