September 11, 2013 marks the 12th anniversary of the nearly 3,000 people killed when planes were hijacked and crashed into the World Trade Center, the Pentagon and a field in Pennsylvania.

Most people still remember exactly what they were doing when they learned that the twin towers had been attacked and New York City was in a state of turmoil.

Although NYC is in the ongoing process of building the area around Ground Zero, there will forever be a hole in the sky for New Yorkers.

Today those affected by the tragedy gather at the National September 11 Memorial plaza in Manhattan for the annual reading of victims' names from both the 1993 and 2001 attacks on the World Trade Center, according to the Chicago Tribune.

Keeping to the tradition established last year, no public officials will speak at the ceremony. Last year, former New York Mayor Rudolph Giuliani, his successor Michael Bloomberg, Police Commissioner Raymond Kelly and other city and state leaders were in attendance for the gathering.

Bagpipes played and youth choir sung by the two reflecting pools where the twin towers used to stand. People spoke about the loved ones they lost in the attack. One of the 250 people chosen to read names said, "To my nephew Michael Joseph Mullin, we miss you and think of you every single day."

Another woman said, "You're gone but not forgotten," referring to her lost cousin.

The ceremony also included a citywide moment of silence at 8:46 a.m. EDT, the same time 12 years ago that American Airlines Flight 11 crashed into the North Tower, followed by a second pause at 9:03 a.m. when United Airlines Flight 175 hit the South Tower.

Further moments of silence were observed at 9:37 a.m., when American Airlines Flight 77 hit the Pentagon, at 9:59 a.m. when the South Tower fell, at 10:03 a.m. when United Flight 93 hit the ground near Shanksville, Pennsylvania, and at 10:28 a.m., when the North Tower collapsed.

One World Trade Center was the tallest building in the Western Hemisphere at 1,776 feet.

Nineteen hijackers died in the attacks staged by Osama bin Laden and al Qaeda, which led to the United States' war in Afghanistan and indirectly to the invasion of Iraq.

Several cities will hold ceremonies that will consist of 21-gun salutes, moments of silence and memorial services to remember and honor those who lost their lives, including the police officers and firefighters who risked their own and died trying to save victims of the attacks.

Can you believe it has been 12 years since the 9/11 attacks? For many the day is still so clear and will most likely never become a distant memory.

Do you remember what you were doing on September 11, 2001 when you learned of the attacks? Let us know by leaving a comment below.