The Earth's magnetism results from vast electrical currents generated by motions in our planet's liquid metal core. The Earth's magnetic field is a fundamental aspect of our natural environment that provides protection from the charged particles that stream from the sun. Yet it is far from steady – the magnetic pole in the northern hemisphere is moving towards Siberia and the field strength is being used in the South Atlantic. There are many unresolved questions regarding the mechanism of generating the field and driving its changes. This talk will provide an overview of the Earth's magnetism, describe recent progress using magnetic observations from satellites to track its changes in great detail, and discuss what this is teaching us about the electromagnetism of Earth's deep interior.