In a recent paper published in the journal ACS Nano, an international team of researchers reveled that they had invented a tiny, corkscrew-shaped propeller, just 400 nanometers long, and 70 nanometers wide. The width is about 100 times smaller than a red blood cell. They're even smaller than any known swimming micororganism, according to the paper's abstract.

The tiny size means that the propeller can go where no robot has gone before—inside human cells and connective tissue. The researchers hope that the product will eventually be used for medical applications, delivering drugs or radiation to the precise location in the body where it is needed.

“One can now think about targeted applications, for instance in the eye where they may be moved to a precise location at the retina,” author Peer Fischer said in a press release.

The researchers tested the silica and nickel propellers by piloting them through gels that appear in the eye and skeletal tissue, which it was able to move through without problems, even though it does have some trouble with other types of fluids, as Gizmodo reports:

Using a weak, rotating magnetic field, the researchers are able to get the corkscrew nanopropeller spinning in fluid, propelling it forward. The nanobot is so small, it gets tripped up by molecules of pure water—Brownian motion, the random low-energy wiggling of H2O molecules, are enough to deflect the little submarines.

Having these tiny missiles prescribed by the doctor is still something for the future. In the meantime, plenty of other medical competitors are working their way down the R&D pipeline, including robot surgeons that can work inside astronauts and micro-rocket drug delivery systems. Tomorrow’s medicine looks like it’s going to be a whole lot smaller.