Nanotechnology can be defined as “the art and science of manipulating matter at the nanoscale (down to 1/100,000 the width of a human hair) to create new and unique materials and products. But the nano scale is not just small; it is so small that even the most powerful conventional microscopes cannot see it. A molecule of sugar measures 1 nm, about as big in relation to an apple as the apple is in relation to the earth. One molecule of DNA is about 2.5 nm wide. A human hair is huge by comparison, about 50,000 nm wide. The head of a pin is about 1 million nm wide.
This radical reduction in size means that seemingly ordinary materials may behave completely differently than in their larger bulk or macro form. Due to their small size, nanoparticles can cross biological membranes, cells, tissues and organs more readily than larger particles. Once in the blood stream, nanomaterials can circulate throughout the body and can lodge in organs and tissues including the brain, liver, heart, kidneys, spleen, bone marrow and nervous system. Once inside cells, they may interfere with normal cellular function, cause oxidative damage and even cell death.