And importantly, it's much faster than conventional methods, which use markers and traps to gradually bind cancer cells. Blood flows quickly, so you're only waiting minutes to pinpoint the cancer. And if you need better results than you got the first time around, you just have to add another chip.

The technique could be the key to a new wave of cancer treatments. If you can single out aggressive cancer cells, you'll have a better sense of how to treat the cancer in question. In an ongoing breast cancer trial, for example, it'll show whether or not blocking a immune signalling molecule might reduce the number of stem-like cancer cells. This won't necessarily lead to cures for stubborn cancers, but it could offer hope in situations where a cancer would otherwise be impossible to stop.