The term StyrofoamTM refers to an extruded polystyrene material developed by Dow; the term is often misused when referencing a type of expanded polystyrene foam that is commonly used to make disposable take-out containers, dinnerware, and packaging materials. Expanded polystyrene products that have the microwave-safe label have been tested for safety in the microwave, and should be safe for use. However, you should avoid putting polystyrene containers in the microwave altogether if you are not sure, and cannot locate a microwave-safe label on the packaging.