Nearly 13 years after the attack that changed our country forever, a museum commemorating 9/11 at ground zero is about to open.

The 9/11 Memorial Museum opens Thursday, May 15th. It will be open privately for six days so those directly affected by the attack can see it before the public opening.

The museum is built almost entirely underground sitting in the footprint of the World Trade Center.

Likely one of the most emotional stops in the museum is an art installation which mimics the blue sky on that fateful morning. Behind it are the still unidentified remains of 9/11 victims. 

"A still shocking statistic is that 1100 family members never got any human remains back to bury, never got to go through the ritual of laying their loved ones to rest. It's not a public space at all, only family members are allowed back behind the wall," said museum president Joe Daniels.