Like any technology, nanotechnology can be used for good and for evil. While nanotechnology will likely lead to exciting new medical treatments and incredibly strong and light materials, it could also be used to produce invisible weapons and for other negative purposes such as spying. Having the lead in nanotechnology could mean military supremacy during this century.
On the positive side, nanotechnology could be used to create tiny machines that scour your body to remove cancerous cells and repair other damage such as clogged ateries. Also, perhaps computers could be made even smaller using nanotechnology, and certainly building materials could be made much stronger an lighter. But at what cost?