Nanotechnology is the engineering of molecularly precise structures and, ultimately, molecular machines. Nanomedicine is the application of nanotechnology to medicine, and the ultimate tool of nanomedicine is the medical nanorobot -- a robot the size of a bacterium.

Although nanotechnology comes with dangers -- some unpredictable -- nanorobotics could also hold the greatest promise for curing disease and extending health span. A “microbivore” robot could act as an artificial mechanical white cell, seeking out and digesting unwanted pathogens including bacteria, viruses, or fungi in your bloodstream. Medical nanorobots could also be used to perform surgery on individual cells. A nanorobot called a “chromallocyte” could extract all existing chromosomes from a diseased cell and insert fresh new ones in their place. Chromosome replacement therapy could correct the accumulating genetic damage and mutations that lead to aging in every one of your cells.

Right now, medical nanorobots are just theory. Building them will require a new technology called molecular manufacturing. But medical nanorobotics could begin to appear in clinical treatment as early as the 2020’s.