(CNN)For more than a century, the teeny tiny coffin hid a big secret: the youngest mummy in ancient Egypt.
British archaeologists revealed this week that a miniature coffin under their care contained the youngest human fetus ever uncovered in ancient Egypt.
"This discovery is the only academically verified specimen to exist at only 16 to 18 weeks of gestation," University of Cambridge said in a statement.
The coffin made of cedarwood dates to around 664-525 BC, and highlights the value of burial rituals in ancient Egypt, even at such a young age.
Dug up decades ago
The diminutive coffin was excavated in the Egyptian city of Giza in 1907.
But researchers left it alone for years, believing the small bundle inside contained gruesome mummified organs from embalming procedures.
An X-ray imaging at the Fitzwilliam Museum, which is the university's antiquities facility, was inconclusive, the university said.
A micro CT scan at Cambridge University's zoology department later revealed the first pictures of a tiny mummified human body held within undisturbed wrappings.
"Five digits on both hands and feet and the long bones of the legs and arms were all clearly visible," the university said.
"Although the soft skull and pelvis were found to be collapsed, the categorical consensus was that inside the bundle was a human fetus estimated to be of no more than 18 weeks gestation."
The fetus, whose gender is unclear, is believed to be the result of a miscarriage. Archaeologists could not determine why it was not carried to full-term.
King Tut buried with 2 fetuses
This is not the first time mummified ancient fetuses have been discovered in Egypt.
But previous ones have been older, and include two found in coffins within King Tut's tomb. Those were estimated to be between 25 to 37 weeks old.