After 27 hours in surgery, a pair of twin boys joined at the head in the US have been successfully separated.
Anias and Jadon McDonald, both 13 months old, underwent the life-threatening operation at the Children's Hospital at Monteiore Medical Center in the Bronx on Thursday and Friday (local time).
They are now recovering in hospital as they begin their new lives apart.
Their surgeon, Dr James Goodrich, said he considered stopping halfway through the operation when he realised the boys shared more brain tissue than was expected from 3D imaging.
The separating procedure took around 16 hours, with another several hours of plastic surgery needed to rebuild the skulls and make them whole.
Anias and Jadon had had three previous surgeries to gradually separate certain areas of the brain.
Jadon finished first, at around 7am, with surgeons finishing on Anias at around 1pm.
The two were then reunited with their parents at the paediatric intensive care unit.
Dr Goodrich is one of the world's leading experts on so-called craniopagus surgery. This was his seventh such surgery performed by Dr Goodrich and the longest. It is only the 52nd craniopagus separation surgery worldwide since 1952.
Parents Nicole and Christian decided to go ahead with the operation, even though it carried major risks, including death or long-term brain damage for the boys.
But 80 percent of twins joined at the head will die if not separated by age two.
"TWO SEPARATE BABIES!!!...and yet I ache with the uncertainty of the future," Ms McDonald wrote on Facebook. "I didn't cry until the surgeons left the room. I was barely able to even utter the words 'thank you' because of the pit that still sits heavy in my stomach.
"We are standing on the brink of a vast unknown. The next few months will be critical in terms of recovery and we will not know for sure how Anias and Jadon are recovering for many weeks."
Before the 1980s, it was accepted practice to sacrifice one child to save the other in surgery, though many times both died. If one survived, he or she often had long-term brain damage.
Dr Goodrich's mantra is: "Take it easy and slowly and carefully." He has never had a conjoined twin die during the operation.