Animals rely on senses to perceive the surrounding physical world. Magnetic sensing, or the ability to detect the Earth’s magnetic field (magnetoreception), is one of the most controversial animal senses. The notion that animals can detect the Earth’s magnetic field was once ridiculed, but is now a well-established fact. However, the nature of this enigmatic sense has remained a fascinating and unresolved biological mystery. For centuries, determining how animals can detect almost imperceptible gradients in Earth’s magnetic field and orient themselves has advanced slowly, making it one of the most challenging tasks in biology, or even in science in general.

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Different from conventional approaches, we utilized a strategy that combined theoretical postulation, genome-wide screening, computational modeling and experimental validation in an attempt to reveal a fundamental mechanism for animal magnetic sensing. We have identified a magnetic receptor (designated as MagR) in animals and a rod-like protein complex magnetosensor. The magnetosensor system is a nano-scale biological compass consisting of photoreceptor Cryptochromes and magnetoreceptors, and has intrinsic magnetic polarity in alignment with magnetic fields, including the Earth’s geomagnetic field.