Someday there may be robots that flow in our blood killing off viruses and helping to repair cells. Computers are also constantly shrinking and nanotechnology is helping to create trasistors only 150 nanometers long. This allows for more memory at faster speeds. Today, micromaching and nanotechnology is very basic. The goal is to make precise products.
Nanotechnology does has some main drawbacks.
Scientists are just beginning to manipulate atoms and until replicators on the atomic level are created, it will be very expensive. There are also many concerns on whether scientists can control the bonding of atoms to each other and whether they will stay that way through temperature changes. Genetics can also use nature's inventions and inprove upon them to create bio-nanomachines. Altering existing systems is a lot cheaper and easier than building a whole new one.