The cover page of Physical Review Letters this week is devoted to work by Jianming and Martin. The cover shows a schematic of their quantum interferometer model of a chemical compass, which they propose is used by birds and other species for efficient navigation. The spin-dependent chemical reaction channels lead to an observable that indicates the direction of the magnetic field. You can read the complete story in Jianming Cai and Martin B. Plenio, Phys. Rev. Lett. 111, 230503 (2013).
And the picture: