Sharon Petzold

On the 15th anniversary of the attack, survivors and first responders share their vivid recollections of the day that changed the world.

Astrophysicists show how black holes might hold answers to how the universe evolved, leading to life on Earth and, ultimately, the human race.

The ocean's predators use their remarkable weapons and skills to hunt or defend themselves against other hungry predators.

100 years after an iceberg defeated the 882-foot luxury liner on its maiden voyage, scientists and historians are still exploring the Titanic. Armed with modern camera technology, submersibles were sent down to the ship's final resting place with the hope of capturing HD 3D visuals of the wreckage, in order to support or even confirm theories about the damage that took the boat down. Now, History Channel has brought some of that footage home in this 45-minute TV special, presented in 3D so that future generations can see it for themselves.

The Sept. 11, 2001, attack on the Pentagon is recalled via the first-person accounts of Pentagon personnel, first responders, aviation experts and journalists. Included: Department of Defense footage from inside the Pentagon.

To commemorate the 75th anniversary of D-Day, this special presents the key events of the Allied invasion of Nazi-held Europe and the subsequent battles that captured the control of the Normandy coast. Some of the last surviving veterans recall in detail the terror, patriotism and drama from the frontlines of war. This special also honors the diverse backgrounds of all who served.