An iPod Nano is not Nano
For years, we have been studying materials in two ways. First, you can talk about macro-scale materials, which basically means anything you can see. Second, you can talk about the "chemistry" of materials, which means dealing with things on an atomic or molecular level. But really, there is a strange middle ground somewhere in there. For example, if you get a sample of Gold that is nanometers wide, it no longer follows the rules of a macroscopic piece of gold, but it can't just be explained as an atom of gold. Materials in the nano-scale often exhibit unique properties due to their high surface area to volume ratios, such as increased conductivity, strength, and differences in optical properties. So you can change a material's properties just by changing its size! Now that is exciting!
Furthermore, many key biological players such as DNA and proteins are nano-sized, so this ability to manipulate materials on the nano-scale has exciting implications for the medical field. Imagine a drug that can seek out a particular type of tissue or cell to act upon. Such innovations are not far off.
Picturing things on the nanoscale can be a challenge, because a nanometer is actually smaller than the wavelength of visible light. This means we can't see nano-scale objects with our eyes or with a traditional light microscope. The chart below shows a variety of common items and their comparative sizes. Notice that microscopic items like cells are still thousands of times larger than a nanometer.