Downtown office workers flee the clowds of smoke that swirled through the streets of lower Manhattan when the towers crumbled.

SAY NO TO TERRORISM!

People gathered in Federal Plaza to offer aid on the first afternoon. Thousands of New Yorkers stood in lines all over the city to donate.

Shoes, left by people running from the burning buildings, hang from branches.

Firefighters and rescue workers worked 24/7 to save lives in lower Manhattan. More than 300 firefighters -- in some cases, entire stations -- were killed in the collapse of the World Trade Center.

Dense smoke and bright lights created one haunting image after another