What are Living Compasses

What do cows standing in a field, a flock of migrating birds, and bacteria have in common?
They all have an unerring sense of where true north (also called magnetic north) lies. How they do this is still a mystery, but scientists believe it may have something to do with a built-in compass the creatures possess.
A recent study on a certain kind of bacteria discovered that the organisms have small particles of magnetite (iron oxide) inside them, and this may very well be responsible for their ability to find north.
The particles in these bacteria line up with earth's magnetic field.
Scientists have also found these magnetic particles near the brains of bees, birds, and trout.