Mount Vesuvius erupted in 79 A.D. killing thousands of people and burying at least four Roman settlements.
The volcanic ash also buried people in the process preserving many victims - the most famous being the victims in Pompeii. However, there were also victims in the town of Herculaneum.
Among the remains in Herculaneum, there was one victim whose parts were unusually preserved. The victim was discovered in the 1960s. He was a young man in his 20s who had died facedown and splayed out on a wooden bed. A strange black matter was recovered from the man's remains and researchers began to further study it.
The researchers discovered that a process called vitrification had turned the man's brains into glass. Vitrification occurs when intense heat turns tissue into a glassy substance. The shards of black matter from the victim contained tubular structures that were identified to be neurons or brain cells.
Researchers believe that the source of the neurons could be the victim's brain and spinal cord. Hot volcanic ash froze the man's neurons and then subsequent cooling resulted in the transformation of tissue to glass.
The research was first published in the New England Journal of Medicine in 2020. The findings were described to be the best example in archaeology of well-preserved brain tissue. It is also the first discovery of an ancient human brain that has been vitrified by heat.