Fish do it; birds do it; humans do it; even bacteria do it. They all detect the Earth's magnetic field. But we actually know very little about HOW these organisms do it. Humans use compasses, and in some cases, other organisms may take a similar approach—such as microscopic bacteria that rely on bits of rust to point them in the right direction. But in other cases, mother nature seems to have come up with some totally radical techniques for detecting magnetic fields. Check out this week's podcast to learn more. My guest on the podcast, science writer Davide Castelvecchi, also wrote a great piece on this topic in Scientific American.