By building its compass out of crystals that are of just the right size to exist as stable, single magnetic domains, the bacterium makes the best use of every bit of iron it lays down.

• 藉由选择大小刚好，具有稳定、单一磁区的晶体来当作罗盘，这些细菌对于所选用的每一分铁质，都做了最佳应用。