Nanotechnology is the understanding and control of matter at the nanoscale, at dimensions between approximately 1 and 100 nanometers, where unique phenomena enable novel applications. Matter can exhibit unusual physical, chemical, and biological properties at the nanoscale, differing in important ways from the properties of bulk materials, single atoms, and molecules. Some nanostructured materials are stronger or have different magnetic properties compared to other forms or sizes of the same material. Others are better at conducting heat or electricity. They may become more chemically reactive, reflect light better, or change color as their size or structure is altered. Although modern nanoscience and nanotechnology are relatively new, nanoscale materials have been used for centuries. Gold and silver nanoparticles created colors in the stained-glass windows of medieval churches hundreds of years ago. The artists back then just didn't know that they were using nanotechnology to create these beautiful works of art!