Tomorrow is the 25th anniversary of the 9/11 terrorist attacks, and we're still working to identify the remains of victims killed on that horrible day. Thanks to advancements in DNA technology and the use of genetic genealogy (which uses DNA and family tree research), the New York City Office of the Chief Medical Examiner and NYPD identified a woman who died that day back in August.

Here's more:

Twenty-five years after the September 11, 2001 attacks, New York City is still working to formally identify all of the nearly 3,000 people killed at the World Trade Center.

Now, for the first time, the city's Office of the Chief Medical Examiner and the NYPD Detective Bureau have identified a 9/11 victim using genetic genealogy, which combines DNA testing with family tree research, ABC News has learned.

The family of the newly identified victim, who was an adult female, declined to publicly come forward.

Dr. Jason Graham, New York City's chief medical examiner, also told ABC News that the work is a "breakthrough." 

A forensic anthropologist with the medical examiner, Dr. Jennifer Odien, said the method is promising and may identify more victims in the future. "Not every case is going to be able to go through genetic genealogy, but we do have DNA profiles that are not matching to our reference samples, so that's the group right now that we're focusing on and that hopefully is going to yield more positive results," she said.

To put this into perspective, 2,753 people died at the World Trade Center. This includes first responders and the passengers and crews of American Airlines Flight 11 and United Airlines Flight 175. To date, authorities have identified only 1,654 victims.

Almost 1,100 victims are still waiting to be identified, as are their families, who have waited a quarter century for closure.

New York City's Office of the Medical Examiner has vowed to never stop testing and identifying victims. Despite that promise, conditions at Ground Zero mean it's likely some victims will never be formally identified. However, evolving science and technological advancements means there's still hope.