In the 10 years since the attacks of 9/11, much has changed in the world. Led by the United States, western nations invaded and occupied Afghanistan and later Iraq, removing their rulers and unleashing sectarian violence and insurgencies. Hundreds of thousands of soldiers and civilians have lost their lives at a cost of trillions of dollars, and western military forces remain in both countries. A third war, the War on Terror, has driven changes in the U.S. that have pushed against the limits of what American society will accept in return for security -- measures such as pre-emptive military strikes, indefinite detentions, waterboarding, wiretapping, and invasive airport security systems. As we remember those lost on September 11, 2001, and construction of the new skyscrapers in Manhattan nears completion, most U.S, troops are scheduled to leave Iraq by the end of this year and Afghanistan by 2014. Here is a look at some of the events of the post-9/11 decade, and some of the progress still being made. Mariah Williams, 17, was one of the students inside the classroom at Emma E. Booker Elementary school in Sarasota, Florida, with President George W. Bush on the morning of September 11, 2001 (inset photo). Williams, photographed here in that same classroom on Wednesday, Aug. 24, 2011, was reading aloud to Bush, along with classmates, when then White House Chief of Staff Andrew Card whispered into Bush's ear that a second plane had hit the World Trade Center in New York City. A test of the Tribute in Light rises above lower Manhattan, on September 6, 2011, in New York City. The memorial, sponsored by the Municipal Art Society, will light the sky on the evening of September 11, 2011, in honor of those who died ten years ago in the terror attacks on the United States. One World Trade Center has reached the 80th floor in this aerial photo, on August 30, 2011 in New York City.