The countries of Europe and the eastern Mediterranean and Middle East operate on a 220 volt electrical system. This means that electrical devices designed for use in the US will not work without the appropriate conversion devices. Trying to use electrical devices without a transformer and/or converter will result in damage to your device. Even with a transformer, some appliances, such as electric blow dryers, will not work well. Converters and transformers are available in the US at hardware stores and electrical supply stores. Adapters for plugs are also available and these will be necessary. Always make sure you purchase a plug suitable for the country to which you are traveling and be sure that the transformer is heavy enough to handle the wattage of the device you will be using. Laptop computers, cell phones, tablets, etc., often come equipped with a built-in transformer in their charging cords and can be operated on any system between 110 and 240 volts as long as the proper plug adapter is used. Check with your computer dealer to determine if you can use your laptop without a transformer.