In two decades since 9/11, lots of things have changed. The constant? Lasting uncertainty.
After the 2001 attacks, companies began looking for new ways to make their workers feel safe. Keycards and ID badges took off.
Many have been diagnosed with cancer. The exposure to toxins from the pulverized buildings "has a really, really long tail," a doctor says.
The developer of the World Trade Center hopes to recover billions of dollars from United, American, Boeing and other aviation companies to pay for WTC's destruction in the 9/11 terrorist attacks.
Before 9/11, many local TV broadcasters transmitted from the World Trade Center. Now, they are being wooed back, but there's competition from other skyscrapers.