"We have learned a lot in the meantime," confessed a senior German government official, referring to the group, now known as the Hamburg cell.

He was the first member to apply for a visa in the Hamburg cell.

He is thought to be a key member of the Hamburg cell which masterminded the onslaught.

The Hamburg cell was born at this apartment.

Here they formed the secretive Hamburg cell, which also included other minor participants in the 9/11 plot.

"I did one about the Hamburg cell of Al Qaeda."

It was here that the Hamburg cell developed and acted more as a group.

Mr. Atta and two other pilots in the attacks were from the Hamburg cell.

While three major suspects had fled in the days before the attacks, the police questioned several other people associated with the Hamburg cell.

Together, they formed the Hamburg cell and became central perpetrators of the September 11 attacks.