These everyday things didn't exist before 9/11. Now they're trillion-dollar industries.

From the internet cloud and your smartphone to the TSA, daily life in the U.S. has changed dramatically since that awful September day in 2001. In 2001 Microsoft released MSN Messenger and Friendster was in its infancy. Today, Facebook has 2.8 billion users and is valued at more than $1 trillion. The tech giant and other social media apps rely on the cloud and mobile devices for the data that make their algorithms and ad targeting systems so effective. 

Take air travel. Before 9/11, security at airports was mostly privately run, and may have included walking through a metal detector. Passengers could take baseball bats and blades up to 4 inches on the plane; family members could go through security to the gate to say goodbye; identification wasn't always required and nobody took off their shoes. Passengers typically needed to arrive 30 minutes before their flight.