Seventeen years later, more than 1,100 victims of the hijacked plane attacks on the World Trade Center are yet to be identified. But in a New York lab, a team is still avidly working to identify the remains, with technological progress on its side. Day in, day out, they repeat the same protocol dozens of times.

At first, they examine a bone fragment found in the wreckage of the Twin Towers and try to match it with DNA samples. Cut and ground to a fine dust, the remains are then mixed with two chemical products that can expose and then extract DNA. But success is not guaranteed.