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.

SpaceX’s Dragon spacecraft, March 6, 2014. SpaceX's Falcon 9 rocket and Dragon spacecraft launched from Launch Complex 40 at the Cape Canaveral Air Force Station, Florida, for their third official Commercial Resupply (CRS) mission to the orbiting lab on April 18, 2014. Dragon returned to Earth with a parachute-assisted splashdown off the coast of southern California on May 14, 2014. Dragon is the only operational spacecraft capable of returning a significant amount of supplies back to Earth, including experiments. (Photo by Ron Lin/SpaceX Photos)

This October 25, 2014 photo provided by the U.S. Geological Survey shows lava flow advancing across the pasture between the Pahoa cemetery and Apa'a Street, engulfing a barbed wire fence, near the town of Pahoa on the Big Island of Hawaii. Dozens of residents in this rural area of Hawaii were placed on alert as flowing lava continued to advance. Authorities on Sunday, October 26, 2014 said lava had advanced about 250 yards since Saturday morning and was moving at the rate of about 10 to 15 yards an hour, consistent with its advancement in recent days. The flow front passed through a predominantly Buddhist cemetery, covering grave sites in the mostly rural region of Puna, and was roughly a half-mile from Pahoa Village Road, the main street of Pahoa. (Photo by AP Photo/U.S. Geological Survey)

The Boeing 747-8 cargo plane pilot has seen thunderstorms, shooting stars and sunsets from up above the clouds and has looked down on mountaintops, carpets of cloud and cities lit up at night. The incredible pictures give a glimpse of the view from the pilots are treated to every day. Here: Shooting stars over India. (Photo by Christiaan van Heijst/Caters News Agency)

A high-kicking Parisian can-can dancer. (Photo by Hulton Archive/Getty Images). 1895

A man is seen trapped amid the debris of an under-construction flyover after it collapsed in Kolkata, India, March 31, 2016. Using saws, small cranes and bare hands, rescuers on Friday cleared the crumbled concrete and twisted steel from an overpass that collapsed onto a crowded Kolkata neighborhood, killing at least 23 people and injuring more than 80. With more than half the debris cleared by Friday morning, 67 people have been pulled out alive, police said. (Photo by Rupak De Chowdhuri/Reuters)

An American flag flutters on a young tree stripped of bark after a massive tornado passed through the town killing at least 116 people May 24, 2011 in Joplin, Missouri. The tornado that ripped through the town of about 50,000 people May 22, is being called the deadliest single tornado in the U.S. in 60 years. (Photo by Julie Denesha/Getty Images)

There are many types of collections. Some are formed by purposefully collecting certain objects, such as stamps or coins. However, some collections are only a byproduct of an obsession, a quirk of mind. For example, Paul Brockmann got into the habit of buying his girlfriend and later his wife a dress every time they went ballroom dancing. It might seem excessive to some, but it was his way of showing his affection. Overtime, this collection grew to be enormous, counting 55,000 dresses in total. Basic math tells us that either they went ballroom dancing three times per day for every day of their lives, or he bought them in huge bundles every time.