Multiple 9/11 memorial ceremonies were held across the country Friday, 14 years after the worst terror attack to ever hit U.S. soil.
Now many have turned the most tragic day into a day of giving back.
9/11 Day on Twitter is an account set up to encourage its followers to do a good deed.
Thousands of rescue teams and their canines scoured through the rubble for survivors.
Now, out of about 100 rescue dogs who responded to 9/11, the only surviving canine, Bretagne, is celebrating her sweet 16.
Bretagne and her owner, Denise Corliss, were part of Texas Task Force 1.
BarkPost Video, which is based in New York, gave Bretagne and her owner, Denise Corliss, an all-expense paid trip to New York City for her big birthday bash.
Along with treats and toys, Bretagne was presented with a cobblestone paver marked with her name at the 9/11 Memorial.
BarkPost also donated $1,000 to Texas Task Force 1 to help train more rescue dogs.
And on the eve of the anniversary, this picture made waves across the Internet - a rainbow appearing to emerge from One World Trade Center in lower Manhattan.