This year a few mice are set to become the first patients for a brand-new kind of heart disease treatment.

It’s a surgery being performed by tiny microsurgeons. The surgeons, called nanorobots, are really tiny groups of magnetically charged particles that band together to break up clogged arteries.

The robot molecules work on blockages in two stages. First they deliver drugs that help soften clogged arteries. Then they charge into battle, drilling in to blast heart blockages apart.

Biomedical engineer MinJun Kim, a professor at Drexel University, is part of the international team of scientists from the U.S., Switzerland, and South Korea who are working on the tech. He says the robots are controlled by harnessing the power of magnetic resonance imaging (MRI), the tunnel-like machines more commonly used for X-ray imaging in hospitals. Working with the nanobots, the MRI machines can serve as a kind of command and control center: both steering and observing the magnetically charged bots as they navigate their way around inside the body.

Kim’s already tried this out in the lab. But it’s a strategy that still needs some fine-tuning before human trials. The nanobots need to perfect their drilling techniques. The plan is to try that out this summer with mice at a national hospital in South Korea. Then the team will move on to testing in rabbits and pigs. If all goes well, by 2019 they’ll be launching the bots into humans (via catheter injection).

Many have tried for years to build nanobots that can serve as minisurgeons inside the body. The robots have been touted as potential solutions for detecting cancer and helping out with eye surgery. Google’s new Verily, the life sciences division of Alphabet, started its own partnership with Johnson & Johnson jnj on surgical robots in 2015 dubbed “Verb Surgical.” But little’s known about how far along Google googl might be with its surgical bots, and there haven’t been any other definitive human trial results just yet.

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Surgeons are already using bigger external robots to assist with heart surgeries. By remote-controlling robotic arms, the doctors can make smaller incisions and more precise movements than they’d be able to using human hands.

WATCH: Surgery goes robotic:

When it comes to the tiny nanobot models that Kim and his team are working on, though, he says “the smaller the better.” That way, after arteries have been blasted and unclogged, the molecules can just swim off the job and biodegrade.