And they're developing breakthroughs for the future.
Some of the faces have changed over the years, but the commitment of the World Trade Center DNA identification team is as focused today as it was in the early days following 9/11.
"We have over 21,000 bits of bone recovered from the World Trade Center, for the 2753 victims," WTC team forensic biologlist Mark Desire said.
Desire oversees the five DNA scientists assigned to the trade center team at the Office of the Chief Medical Examiner. They call it the largest missing persons case ever. Sixty percent of those original 21,000 bone fragments have been identified. More than 4,000 bones remain that could generate DNA profiles of victims.
"These are all bones that have been, previously had DNA attempted multiple times," Desire said. "And hopes what we couldn't do 10 years ago, we're going to be able to do today."
It's all about the ever-improving technology, the research scientists have developed at the facility now allows them to extract DNA from tiny pieces of bone. It's dramatically changed in the past few years.
"We can now take a bone that's chicklet-size, half a gram, and basically put it through our research process and be able to obtain a profile, where before we couldn't," criminalist Sarah Phillips said.
Most of the bones match remains of previously identified victims, but there have been some new identifications, two back in 2009 and one this year.
"The ID process begins with having a reference sample to compare it to," Phillips said. "So we generate DNA profiles from all of the remains that are recovered from WTC and we need to be able to compare them to known samples...known samples being an item that the victim used during their life, a toothbrush, a razor, or a hairbrush, known samples could also include family samples."
The team collected 17,000 reference samples, and every day they test and re-test those thousands of bones.
"The goal is to identify all the victims from September 11th and that's what we're shooting for," Desire said.
And they continue to develop new technology here for the future. They're working on a technique to determine someone's eye color, hair color, skin color from a single bone fragment. Think of what that could do to help identify missing victims in everyday missing persons cases.