Dogs can use their incredible sense of smell to sniff out various forms of cancer in human breath, blood and urine samples. Similarly, in the lab a much simpler organism, the roundworm C. elegans, wriggles its way toward cancer cells by following an odor trail. Today, scientists report a device that uses the tiny worms to detect lung cancer cells. This "worm-on-a-chip" could someday help doctors noninvasively diagnose cancer at an earlier stage.