Scientists say they have gained new insight into what lies at the very centre of the Earth.
Research from China and the US suggests that the innermost core of our planet has another, distinct region at its centre.
The team believes that the structure of the iron crystals there is different from those found in the outer part of the inner core.
The findings are reported in the journal Nature Geoscience.
Without being able to drill into the heart of the Earth, its make-up is something of a mystery.