What exactly is hidden in the pyramids?

They're described as "anomalies," reflecting the nature of the non-invasive technology used to try and see into the stone of the Egyptian pyramids.

But what exactly do the temperature differences reveal? "Unknown internal structures and cavities", reports CNN: voids that could be hidden chambers within the ancient monuments.

The investigation has found one "particularly impressive" anomaly at the Khufu pyramid -- the only one of the Seven Wonders of the Ancient World still standing and the largest Pyramid ever built.

The results have come just two weeks into Operation Scan Pyramids, which will last until the end of 2016. The scientific mission uses "noninvasive visualization techniques," including 3-D scans with lasers and drones, to see inside the pyramids.

Maybe it'll be full of grain.