When Patricia Reilley entered the National September 11 Memorial Museum for the first time last week, she braced herself.
She was about to re-live that day, yet again.
On September 11, 2001, Reilly's younger sister, Lorraine Lee, was working on the 101st floor of the World Trade Center's South Tower.
The 37-year-old worked as an administrative assistant.
While on her bus to work, Reilly saw smoke billowing from the North Tower, and called her sister.
"She told me she had been told to stay at her desk," Reilly said. "I told her I would speak to her later when I got to work."
She never spoke to her sister again.
Later that day, as the disaster unfolded, one of Lee's co-workers, who'd fled the office, called Reilly and asked if her sister was okay.
"I was happy for her," she said. "But it was painful to know that my sister could've gotten out."
Lee's boss was a fire warden, and she stayed behind to help.
Last week during a preview tour, Reilly got her first glimpse of the 9/11 Museum, which is set to open in New York City nearly 13 years after the attacks took place.
The terror attacks destroyed the Twin Towers and killed about 3,000 people, including 2,753 in New York.
After years of delays, the museum will be dedicated on Thursday, and will open to the public on May 21st.
Visitors enter the museum through a pavilion where two tridents, steel beams from the North Tower facade, stand in the atrium.
Down several long ramps, the museum's main exhibitions are located seven stories below the 9/11 Memorial, on the bedrock of the World Trade Center where the Twin Towers once stood.
The exhibitions include tens of thousands of photographs, testimonials, audio and video recordings that tell the story of 9/11 and the days that followed through the experiences of survivors, responders, area residents and eyewitnesses.
"It's a museum about people and stories," said museum director, Alice Greenwald. "You can hear from the people who were there, and when they were there."
Artifacts large and small are everywhere.
A partially burned out and mangled fire engine, Ladder 3, sits near remnants of other equipment used by first responders.
Down below, a portion of the slurry wall, built around the original foundation, and responsible for preventing the Hudson River from flooding the site, remains intact.
For Reilly, the museum's location at the World Trade Center site is especially profound.
"This museum is right in the middle of what it's trying to have people remember," she said.
Reilly has been working for years with various 9/11 family groups to have input into the creation of the museum, she owed that to her sister, she said.
"Long after we're gone, I wanted people to see her name and think about her as a person, along with all the people who died that day," Reilly said.
In a section of the museum focused on security measures then and now, Reilly found something she had been looking for: her sister's picture office ID card.
That and Lee's pocketbook were the only personal items the family ever recovered.
"I'm always amazed that we never got my sister back, but we were able to get these," Reilly said through tears. "These are the things that she had with her at the end."
Reilly and her family are certainly not alone.
Remains haven't been found or identified for some 40% of the people who died at the World Trade Center on September 11th.
Thousands of unidentified fragments of humanity recovered in the years since the attack will be placed in a special repository inside the museum, even though some 9/11 family members vehemently object to the remains being placed in the museum.
Many would prefer to see them honored as part of the 9/11 Memorial above the museum, where the public could pay their respects.
Other controversies surrounding the museum still simmer.
Some object to the $24 admission price for the public, including 9/11 families who've said it makes the museum a "revenue-generating tourist attraction."
Victims' families and several other categories of visitors are allowed to see the exhibit for free.
Revenue generated by the museum, which has a projected $60-million annual operating budget, allows the Memorial fountains and plaza to remain free and open to the public, museum officials have said.
Meanwhile, the museum, a private, not-for-profit institution, is still fighting for federal funding.
Efforts to secure federal funding for the 9/11 museum have been blocked in Congress.
The museum directors had hoped to open three years ago, for the 10th anniversary of the attacks, but the project has endured funding disputes, building delays and even a flood caused by Superstorm Sandy.
When asked what the most contentious issue has been, museum director Greenwald answered, "everything."
Perhaps what will be the most emotional exhibit in the museum wasn't open for the preview tour: the Memorial Hall, which will display portraits of everyone who was lost, along with memories about their lives provided by loved ones.
After the tour, Reilly felt satisfied, if emotional and overwhelmed, that her sister's memory was represented at the museum.
"I succeeded in having her remembered," Reilly said. "That was something that was so important to me."
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