Tributes poured in from around the world to Neil Armstrong, the first man to walk on the Moon, who has died at the age of 82.
The former Nasa astronaut had suffered complications from heart surgery he underwent earlier this month, his family said.
He famously uttered the quote moments after setting foot on the lunar surface: "That's one small step for man, one giant leap for mankind."
US president Barack Obama hailed Armstrong as one of America's greatest heroes.
In a statement issued by the White House, Mr Obama said the crew of Apollo 11 carried with them the aspirations of an entire nation when they set out for the moon in 1969.
He said: "Neil was among the greatest of American heroes - not just of his time, but of all time. When he and his fellow crew members lifted off aboard Apollo 11 in 1969, they carried with them the aspirations of an entire nation.
They set out to show the world that the American spirit can see beyond what seems unimaginable - that with enough drive and ingenuity, anything is possible. And when Neil stepped foot on the surface of the moon for the first time, he delivered a moment of human achievement that will never be forgotten.
"Today, Neil's spirit of discovery lives on in all the men and women who have devoted their lives to exploring the unknown - including those who are ensuring that we reach higher and go further in space. That legacy will endure - sparked by a man who taught us the enormous power of one small step."
Astronomer Sir Patrick Moore said: "As the first man on the Moon, he broke all records. I knew him well. He was a man who had all the courage in the world."
Physicist Professor Brian Cox tweeted: "Sad to hear about death of Neil Armstrong. I do think Apollo was the greatest of human achievements. For once, we reached beyond our grasp."
Armstrong commanded the Apollo 11 spacecraft that landed on the Moon on July 20 1969. He and fellow astronaut Edwin "Buzz" Aldrin spent nearly three hours walking on the Moon, collecting samples, conducting experiments and taking photographs.
Mike Cruise, professor of astrophysics and space research at the University of Birmingham, said: "The people at the front of the race always have to tread on new ground. He led the whole world into a space era of greater proportion than has been achieved by satellites.
"You wonder when his first steps will be followed up. It must have been very awe-inspiring to step on to, essentially, a new planet."
Jamie Burgess, from the UK National Space Centre, in Leicester, said: "I think it is safe to say (he was) a very brave man, a very courageous man. To be able to have that bravery is an incredible quality in a person. He is a fantastic character and will be sorely missed."
An estimated 600 million people - a fifth of the world's population - watched and listened to the first moon landing, the largest audience for any single event in history.
The moonwalk marked America's victory in the Cold War space race that began on October 4 1957 with the launch of the Soviet Union's satellite Sputnik 1.
Armstrong and then wife Janet would later meet Queen Elizabeth and Prince Andrew at Buckingham Palace at a reception following the moon-landing in 1969 during his 22-nation 38-day world tour.
Announcing his death, Mr Armstrong's family said in a statement: "We are heartbroken to share the news that Neil Armstrong has passed away following complications resulting from cardiovascular procedures.
"Neil was our loving husband, father, grandfather, brother and friend. Neil Armstrong was also a reluctant American hero who always believed he was just doing his job."
It continued: "For those who may ask what they can do to honour Neil, we have a simple request. 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 at you, think of Neil Armstrong and give him a wink."
Space agency Nasa tweeted: "Nasa offers its condolences on today's passing of Neil Armstrong, former test pilot, astronaut & the 1st man on the moon. Neil was 82."
Meanwhile, Apollo 11 command module pilot Michael Collins, who was part of the historic moon-landing mission, paid tribute to Armstrong, his former colleague.
He said: "He was the best, and I will miss him terribly."
Former NASA astronaut Harrison Schmitt, who also set foot on the moon, described Armstrong as a "remarkable individual".
He told BBC Breakfast "I remember him as a professional at all times, very mature but also a very warm individual. He did not seek the limelight as some may have."
Portrait of Astronaut Neil A. Armstrong, commander of the Apollo 11 Lunar Landing mission in his space suit, with his helmet on the table in front of him. Behind him is a large photograph of the lunar surface. (NASA)
A group photo of NASA research pilots at the front door of the Flight Research Center headquarters building. In the front row are (left to right) Milt Thompson, Jack McKay, and Bill Dana. All three flew the X-15, and Thompson and Dana were also involved in the lifting body flights. McKay was injured in a crash landing in X-15 #2. Although he recovered, the injuries eventually forced him to retire from research flying. In the back row (left to right) are Neil Armstrong, Bruce Peterson, Stanley Butchart, and Joe Walker. Armstrong and Walker also both flew the X-15. Soon after this photo was taken, Armstrong was selected as an astronaut, and seven years later became the first man to walk on the Moon. Walker made the highest flight in the X-15, reaching 354,200 feet. He then went on to fly the Lunar Landing Research Vehicle, and was killed on June 8, 1966 when his F-104N collided with the XB-70. Peterson made the first flight in the HL-10 lifting body, and was later badly injured in the crash of the M2-F2 lifting body. Butchart flew a wide range of research missions in the 1950s, and was the B-29 drop plane pilot for a number of rocket flight. (NASA)
FILE - This July 20, 1969 file photo provided by NASA shows Apollo 11 commander Neil A. Armstrong inside the Lunar Module while on the lunar surface. Astronauts Armstrong and Edwin E. Aldrin Jr., lunar module Pilot, had already completed their extravehicular activity when this picture was made. First moonwalker Armstrong, first American in orbit John Glenn, Mission Control founder Chris Kraft, Apollo 13 commander Jim Lovell, first shuttle pilot Robert Crippen and others are pushing for a last minute reprieve for the about-to-be-retired space shuttle fleet. (AP Photo/NASA, file)
Portrait of the prime crew of the Apollo 11 lunar landing mission. From left to right they are: Commander, Neil A. Armstrong, Command Module Pilot, Michael Collins, and Lunar Module Pilot, Edwin E. Aldrin Jr. On July 20th 1969 at 4:18 PM, EDT the Lunar Module "Eagle" landed in a region of the Moon called the Mare Tranquillitatis, also known as the Sea of Tranquillity. After securing his spacecraft, Armstrong radioed back to earth: "Houston, Tranquility Base here, the Eagle has landed". At 10:56 p.m. that same evening and witnessed by a worldwide television audience, Neil Armstrong stepped off the "Eagle's landing pad onto the lunar surface and said: "That's one small step for a man, one giant leap for mankind." He became the first human to set foot upon the Moon. (NASA)
Portrait of Astronaut Neil A. Armstrong in civilian clothes. (NASA)
Astronaut Neil A. Armstrong, Gemini 5 backup crew command pilot, sits in the Gemini Static Article 5 spacecraft and prepares to be lowered from the deck of the NASA Motor Vessel Retriever for water egress training in the Gulf. (NASA)
Astronaut Neil A. Armstrong climbs into a boilerplate model of the Gemini spacecraft during water egress training on the Gulf of Mexico. (NASA)
In this photograph, Apollo 11 astronaut Neil Armstrong walks to the flight crew training building at the NASA Kennedy Space Center (KSC) in Florida, one week before the nation?s first lunar landing mission. The Apollo 11 mission launched from KSC via the Marshall Space Flight Center (MSFC) developed Saturn V launch vehicle on July 16, 1969 and safely returned to Earth on July 24, 1969. Aboard the space craft were astronauts Neil A. Armstrong, commander; Michael Collins, Command Module (CM) pilot; and Edwin E. (Buzz) Aldrin Jr., Lunar Module (LM) pilot. The CM, ?Columbia?, piloted by Collins, remained in a parking orbit around the Moon while the LM, ?Eagle??, carrying astronauts Armstrong and Aldrin, landed on the Moon. On July 20, 1969, Armstrong was the first human to ever stand on the lunar surface, followed by Aldrin. During 2½ hours of surface exploration, the crew collected 47 pounds of lunar surface material for analysis back on Earth. With the success of Apollo 11, the national objective to land men on the Moon and return them safely to Earth had been accomplished. (NASA)
Astronaut Neil A. Armstrong, command pilot of the Gemini 8 space flight, sits in the Launch Complex 16 trailer during suiting up operations for the Gemini 8 mission. Suit technician Jim Garrepy assists. (NASA)
Astronaut Neil Armstrong walking through the crowd at the Apollo 11 Twentieth Aniversary Picnic at the Gilruth Center. He is carrying a drink in his hand while talking to the crowd. (NASA)
Astronaut Neil A. Armstrong, Apollo 11 commander, participates in simulation training in preparation for the scheduled lunar landing mission. He is in the Apollo Lunar Module Mission SImulator in the Kennedy Space Center's Flight Crew Training Building. (NASA)
Closeup view of Astronaut Neil A. Armstrong, command pilot of the Gemini 8 space flight, making final adjustments and checks in the spacecraft during the Gemini 8 prelaunch countdown. (NASA)
Composite photo of President Richard M. Nixon as he telephoned "Tranquility Base" and astronauts Neil Armstrong and Edwin "Buzz" Aldrin. The President: "... For one priceless moment in the history of man, all of the people on this Earth are truly one, one in their pride in what you have done and one in our prayers that you will return safely to Earth." Astronaut Armstrong: "...Thank You, Mr. President. It is a great honor and privilege for us to be here representing not only the United States, but men of peaceable nations, men with an intrest and curiosity, and men with a vision for the future. It is an honor for us to be able to participate here today. (NASA)
Astronaut Neil A. Armstrong, wearing an Extravehicular Mobility Unit, participates in a simulation of deploying and using lunar tools on the surface of the moon during a training exercise in bldg 9 on April 22, 1969. Armstrong is the commander of the Apollo 11 lunar landing mission. In the background is a Lunar Module mockup (32240); Astronaut Edwin Aldrin, Apollo 11 lunar module pilot, simulates deplying the Passive Seismic Experiment Package during trainin exercise in bldg 9 (32241); Armstrong is standing beside Lunar Module mock-up, holding sample bags during training exercise (32242); Aldrin and Armstrong during lunar surface training exercise. Aldrin (on left) uses a scoop to pick up a sample. Armstrong holds bag to receive sample. In the background is a Lunar Module mock-up. Both men are wearing the EMU (32244). (NASA)
Suited Astronaut Neil A. Armstrong, wearing an Extravehicular Mobility Unit, participates in lunar surface simulation training on April 18, 1969, in bldg 9, Manned Spacecraft Center (MSC). Armstrong is the prime crew commander of the Apollo 11 lunar landing mission. Here, he simulates scooping up a lunar surface sample. (NASA)
Astronauts Neil A. Armstrong (center), command pilot, and David R. Scott (right), pilot of the Gemini 8 prime crew, are suited up for water egress training aboard the NASA Motor Vessel Retriever in the Gulf of Mexico. At left is Dr. Kenneth N. Beers, M.D., Flight Medicine Branch, Center Medical Office. (NASA)
The research pilots at what in 1962 was called the Flight Research Center standing in front of the X-1E. They are (left to right) Neil Armstrong, Joe Walker, Bill Dana, Bruce Peterson, Jack McKay, Milt Thompson, and Stan Butchart. of the group, Armstrong, Walker, Dana, McKay and Thompson all flew the X-15. Bruce Peterson flew the M2-F2 and HL-10 lifting bodies, while Stan Butchart was the B-29 drop plane pilot for many of the D-558-II and X-1 series research aircraft. (NASA)
The Apollo 11 mission, the first manned lunar mission, launched from the Kennedy Space Center, Florida via the Saturn V launch vehicle on July 16, 1969 and safely returned to Earth on July 24, 1969. The Saturn V vehicle was developed by the Marshall Space Flight Center (MSFC) under the direction of Dr. Wernher von Braun. Aboard were Neil A. Armstrong, commander; Michael Collins, Command Module (CM) pilot; and Edwin E. Aldrin Jr., Lunar Module (LM) pilot. The CM, piloted by Michael Collins remained in a parking orbit around the Moon while the LM, named ?Eagle??, carrying astronauts Neil Armstrong and Edwin Aldrin, landed on the Moon. Armstrong was the first human to ever stand on the lunar surface, followed by Edwin (Buzz) Aldrin. During 2½ hours of surface exploration, the crew collected 47 pounds of lunar surface material for analysis back on Earth. The recovery operation took place in the Pacific Ocean where Navy para-rescue men recovered the capsule housing the 3-man Apollo 11 crew. The crew was airlifted to safety aboard the U.S.S. Hornet, where they were quartered in a Mobile Quarantine Facility (MQF). Here the quarantined Apollo 11 crew members (l to r) Armstrong, Collins, and Aldrin, and U.S. President Richard Milhous Nixon share laughs over a comment made by fellow astronaut Frank Borman, Apollo 8 commander. The president was aboard the recovery vessel awaiting return of the astronauts. With the success of Apollo 11, the national objective to land men on the Moon and return them safely to Earth had been accomplished. (NASA)
Famed astronaut Neil A. Armstrong, the first man to set foot on the moon during the historic Apollo 11 space mission in July 1969, served for seven years as a research pilot at the NACA-NASA High-Speed Flight Station, now the Dryden Flight Research Center, at Edwards, California, before he entered the space program. Armstrong joined the National Advisory Committee for Aeronautics (NACA) at the Lewis Flight Propulsion Laboratory (later NASA's Lewis Research Center, Cleveland, Ohio, and today the Glenn Research Center) in 1955. Later that year, he transferred to the High-Speed Flight Station at Edwards as an aeronautical research scientist and then as a pilot, a position he held until becoming an astronaut in 1962. He was one of nine NASA astronauts in the second class to be chosen. As a research pilot Armstrong served as project pilot on the F-100A and F-100C aircraft, F-101, and the F-104A. He also flew the X-1B, X-5, F-105, F-106, B-47, KC-135, and Paresev. He left Dryden with a total of over 2450 flying hours. He was a member of the USAF-NASA Dyna-Soar Pilot Consultant Group before the Dyna-Soar project was cancelled, and studied X-20 Dyna-Soar approaches and abort maneuvers through use of the F-102A and F5D jet aircraft. Armstrong was actively engaged in both piloting and engineering aspects of the X-15 program from its inception. He completed the first flight in the aircraft equipped with a new flow-direction sensor (ball nose) and the initial flight in an X-15 equipped with a self-adaptive flight control system. He worked closely with designers and engineers in development of the adaptive system, and made seven flights in the rocket plane from December 1960 until July 1962. During those fights he reached a peak altitude of 207,500 feet in the X-15-3, and a speed of 3,989 mph (Mach 5.74) in the X-15-1. Armstrong has a total of 8 days and 14 hours in space, including 2 hours and 48 minutes walking on the Moon. In March 1966 he was commander of the Gemini 8 orbital space flight with David Scott as pilot - the first successful docking of two vehicles in orbit. On July 20, 1969, during the Apollo 11 lunar mission, he became the first human to set foot on the Moon. (NASA)
US aviator and former astronaut Neil Armstrong speaks at the Congress Meet the Future, Science & Technology Summit 2010 at the World Forum in The Hague on November 18, 2010. AFP PHOTO/ANP/MARCEL ANTONISSE netherlands out - belgium out (Photo credit should read MARCEL ANTONISSE/AFP/Getty Images)
OLUMBUS, OHIO - FEBRUARY 20: In this handout provided by NASA, Apollo 11 Astronaut Neil Armstrong speaks during a celebration dinner at Ohio State University honoring former U.S. Sen. and astronaut John Glenn's 50th anniversary of his flight aboard Friendship 7 on February 20, 2012 in Columbus, Ohio. Today marks the 50th anniversary of Glenn's historic flight as the first American to orbit Earth. (Photo by Bill Ingalls/NASA via Getty Images)