President Obama and a number of other big shot politicians are joining 9/11 victims' families and first responders at the National 9/11 Memorial Museum this morning for the official dedication ceremony. (The museum won't open to the general public until next week, May 22nd.) The ceremony is now underway, and NBC New York is streaming video of the proceedings:

In addition to audio and visual testimonials from survivors and first responders, the museum displays powerful remnants of the old World Trade Center, including mangled pieces of steel facade, an elevator motor, part of a broadcast antenna and the slurry wall, as well as wrecked fire engines and pieces of plane. Here are some photos that were released yesterday.

Gothamist reporter Christopher Robbins is at the ceremony this morning, so check back later for his account of the proceedings.