It was one of the few moments in modern history when the world held its collective breath, watching on black-and-white TV sets as U.S. astronauts Neil Armstrong and Buzz Aldrin became the first people to set foot on the moon.

It was 45 years ago Sunday that Apollo 11 made its historic moon landing during an eight-day flight that would redefine the limits of human space travel. All these years later, Armstrong and Aldrin remain part of an elite group: less than a dozen other people have since walked on the surface of the moon.

CTVNews.ca has compiled 4 things to know about the milestone anniversary:

Celebration over social media

No anniversary today can be marked without acknowledgement over social media, which is why the Smithsonian’s National Air and Space Museum is recreating the journey over Twitter. For those who want to relive the event – or see it for the first time -- NASA TV will broadcast restored footage of the moon landing, beginning at 10:39 p.m. EDT, marking the exact time Armstrong took those famous steps onto the moon’s surface.   

Wink at the moon

This is the first time a major Apollo 11 anniversary will take place without Armstrong, who died in 2012. At the time of his death, his family had a simple gesture in mind to mark Armstrong’s “giant leap” for mankind.

“For those who may ask what they can do to honour Neil, we have a simple request,” the family said in a statement on Armstrong’s death. “Honour his example of service, accomplishment and modesty, and the next time you walk outside on a clear night and see the moon smiling down on you, think of Neil Armstrong and give him a wink.”

Meanwhile, Armstrong’s fellow crew members -- Buzz Aldrin and Michael Collins, the Apollo 11 command module pilot who orbited the moon -- are set to attend a ceremony Monday at Florida’s Kennedy Space Center as NASA renames the Operations and Checkout building in honour of Armstrong.  

Buzz Aldrin: Space ambassador

Aldrin, now 84, has also been actively celebrating the historic journey. Last week, he asked the public to send him stories about where they were on July 20, 1969, when he was “out of town.”  

The request elicited responses from the likes of Tom Hanks and London Mayor Boris Johnson, who as a five-year-old, watched the landing on a black-and-white TV at an English farmhouse. “I knew immediately it was the most exciting things that I’d ever seen,” Johnson said.  

In a video message posted on Youtube, Aldrin said today he considers himself a “global statesman for space.” Aldrin spends most of his time travelling the U.S. and elsewhere to remind people about the accomplishments of NASA’s space program.

“I feel we need to remind the world about the Apollo missions and that we can still do impossible thing,” he said.  

The next 'giant leap for mankind'

Today, the future of space exploration has shifted, with goals reaching beyond the moon-- namely to Mars.

Mars One, a non-profit organization recruiting civilians for a one-way mission to the red planet, says it plans to send a crew of four to depart every two years starting in 2024. The goal of the mission is to establish a permanent human colony on Mars.

Of the approximately 200,000 people who applied internationally for the one-way trip, more than 8,000 were Canadian. Since then, about 75 Canadians have made the cut to move onto the next selection round.

NASA has also been tasked with trying to wrangle an asteroid, with the hope that asteroids will one day serve as stepping stones to Mars.  

With files from The Associated Press