Scientists say they have identified magnetic cells in fish that allow them to accomplish remarkable feats of navigation by sensing Earth\'s magnetic fields. Researches examined rainbow trout, which can unerringly swim back to their original hatching ground after spending 3 years at sea and travelling as much as 200 miles from home, Science Now reported. For the first time in any animal, scientists have identified magnetic cells in the fish that respond to the planet\'s fields, a finding that could help researchers understand magnetic sensing in a variety of creatures, including birds. \"We think this will really be a game changer,\" earth scientist Michael Winklhofer at Ludwig Maximilians University in Germany said. \"To study magnetic sensory cells, you have to be able to get hold of them first, and that\'s what we\'ve finally developed a way to do.\" The challenge is that magnetic cells are few and far between in an animal; if they were clustered together, they would interfere with each other\'s magnetism. \"If you have a tissue containing these cells, it\'s likely that only one out of 10,000 cells is magnetic,\" Winklhofer said. \"That makes it very hard to do any research.\" The scientists placed a suspension of rainbow trout cells under a microscope that had a magnet rotating around the cell sample, suspecting cells containing magnetic particles would slowly rotate with the magnet. Cells that rotated were transferred to individual glass slides to study them further under the microscope. \"This result is really a step beyond anything we\'ve done before,\" said ecologist Michael Walker of the University of Auckland in New Zealand, whose initial experiments homed in on trout\'s noses as the site of tissue containing magnetic particles. \"The idea that they came up with here is just great and it worked like a charm.\"