A man who died in the 9/11 World Trade Center terrorist attacks in New York 17 years ago has been positively identified this week - after several previous attempts had failed.
It's the latest breakthrough in a huge DNA testing project to try and identify every single person who lost their life in the attack.
But there are around 1,100 people still unaccounted for after the 2001 attack.
Using a fragment of bone, scientists eventually managed to extract enough DNA to identify the victim as Scott Michael Johnson, a 26-year-old securities analyst who worked for investment bank Keefe Bruyette and Woods.
On the day of the 9/11 attacks, Johnson was working on the South Tower's 89th floor when it was struck by the second plane used in the horrific terrorist incident.
Johnson is the 1,642nd person experts have been able to identify - just over half of those thought to have been killed.
So far, they have given closure to around 60% of the families who lost loved ones on September 11th. They are doing this by subjecting the remains that they have to state of the art DNA testing methods.
The team at the New York medical examiner's office are working their way through 22,000 human remains with the intention of finding everyone who died that day. The remains are often difficult to determine because of their exposure to extreme heat, jet fuel, and fire.
Chief Medical Examiner Barbara Simpson said: "In 2001, we made a commitment to the families of victims that we would do whatever it takes, for as long as it takes, to identify their loved ones,
"This identification is the result of the tireless dedication of our staff to this ongoing mission."
Scott Michael Johnson was one of the three children of Ann and Thomas Johnson.
His father is a board member of the National September 11th Memorial and Museum in New York.
He told the New York Times: "His friends reported at his memorial service on the incredible love and support that he gave to them, that in a sense went even beyond our understanding of him,
"He was one of the kindest people that anyone around him had ever known. The pain of losing someone like that was tremendous."
His mother said that the discovery has provided them with closure, but also brought home the finality of their son's death.
She said: "You get pulled right back into it and it also means there's a finality. Somehow, I always thought he would just walk up and say, 'Here I am. I had amnesia.'"
The terrorist attacks that brought down both of the Twin Towers are thought to have killed around 3,000 people in total.