1st prize in the People Observed Portraits Stories category. Carla Kogelman, the Netherlands. The photo shows Hannah and Alena, two sisters living in the rural village of Merkenbrechts, Austria. (Photo by Carla Kogelman/World Press Photo)

Contestants walk on stage during the “mini-miss” beauty contest in Bobigny, Paris suburb, September 22, 2012. The competition is open for girls aged 7 to 12. (Photo by Benoit Tessier/Reuters)

In this photo provided by World Press Photo, the 1st Prize Daily Life Single of the 2011 World Press Photo Contest by Omar Feisal, Somalia, Reuters, shows a man carrying a shark through the streets of Mogadishu, Somalia, September 23, 2010. (AP Photo/Omar Feisal/Reuters)

Wirittorn Narapatarapimol (Belle) a Miss Tiffany Universe contestant tries on earrings in a private dressing room on May 15, 2009 in Pattaya, Thailand. The Miss Tiffany Universe contest has been running for 12 years, with all contestants transexuals or transvestites, aiming to promote human rights for the transgender population in Thailand. In Thailand transexuals are considered a third gender given the Thai name “Katoey”. (Photo Paula Bronstein/Getty Images)

“The Last Pollen Spore Preparing to Leave a Ladybug Trying to Hold On, Because It Didn't Want to Be Alone”. Photo by Hiep Nguyen Hoang (Hanoi, Vietnam). Photographed in Hanoi, Vietnam, April 2012.

The National September 11 Memorial & Museum (branded as 9/11 Memorial and 9/11 Memorial Museum) is the principal memorial and museum commemorating the September 11 attacks of 2001, which killed nearly 3,000 people, and the World Trade Center bombing of 1993, which killed six. The memorial is located at the World Trade Center site, on the former location of the Twin Towers, which were destroyed during the attacks. The World Trade Center Memorial Foundation was renamed the National September 11 Memorial & Museum at the World Trade Center in 2007.

Last weekend, the National Building Museum in Washington, D.C., opened a 10,000 square-foot ball pit to the general public, and everyone cheered that, finally, someone made their childhood dreams come true.