Nano: A unit of measurement for geometrical dimensions.1 nanometer is one-millionth of a millimeter, which is 1 nanometer, which is one-billionth of a meter. Nanostructures usually refer to microstructures with a size below 100 nanometers. Which of the following statements about nanometers is correct? ['A nanometer is a unit of length.', 'One hundred thousand nanometers equal one decimeter.', 'Nano is a very advanced technology that is now widely used in many areas of production and life.', 'Nano usually refers to a very tiny structure.']