The lungs are one of the major sites of metastasis—the spread of tumor cells to far-flung organs. To help protect the lungs (blue) from this deadly process, bioengineers have created microscopic drug depots (red) to focus the effect of anti-cancer drugs that may have limited or toxic effects when delivered to the whole body.

In the future, these microparticles could be administered with technology as simple as an inhaler, buying the body time to build up resources to fight or prevent this fatal migration.