The eruption of Mount Vesuvius 2,000 years ago turned a victim’s brain tissue into glass. Scientists say they have figured out how this unusual phenomenon occurred.

It was a surprising discovery when scientists examining the remains of a man who died in bed in the ancient city of Herculaneum after Italy's Mount Vesuvius erupted in 79 AD found dark fragments resembling obsidian inside his skull.

The only known case of a human brain being turned to glass, that of a man caught in the 79 AD eruption of Vesuvius at the Roman town of Herculaneum near Pompeii, has been solved. The man's brain turned to glass due to the extremely rapid cooling that ensued after a white-hot cloud of ash engulfed him,