The only full-body photograph of Neil Armstrong on the moon shows him working at the Apollo 11 lunar module "Eagle." The first man to set foot on the lunar surface was inadvertently captured on film by Buzz Aldrin, who was tasked with taking a series of panoramic photos.

Buzz Aldrin, reflecting on the passing of his former crewmate, described Neil Armstrong as "the best pilot I ever knew." Before becoming an astronaut, Armstrong was a naval aviator and research pilot. Here he is seen in the X-15 rocketplane, one of over 200 aircraft he flew.

Neil Armstrong was selected as an astronaut with NASA's second group of astronauts in 1962. They called themselves "The Next Nine," following the "Original 7" Mercury astronauts. (Armstrong is first from the left in the top row.)

Of "The Next Nine" (seen here surrounding a mockup of the Apollo command module), all but three flew to the moon, and three walked on its surface, including John Young (second from left), Charles Conrad (fourth from left) and Armstrong (fifth from left).

Before ever flying in space, astronauts had to go through basic training. Here Neil Armstrong is seen working with parachute lines.

John Glenn (left), the first American astronaut in orbit, and Neil Armstrong, the man on the moon, together during survival training.

Neil Armstrong's first flight into space was as command pilot of Gemini 8, the sixth flight of NASA's two-seater spacecraft. Armstrong's crewmate was David Scott (right). Scott would later become the seventh man to walk on the moon.

A rare gag photo taken in November 1965, the Gemini 8 prime crew — David Scott and Neil Armstrong (front row) — is seen with their backups, Richard Gordon and Charles Conrad (who would fly together on Gemini 11 and Apollo 12).

Armstrong was 35 years old when he commanded Gemini 8. He was assigned to the mission in September 1965, and was tasked with the first-ever rendezvous and docking in orbit. "We thought of it as being an absolutely super flight with great objectives, and really loved the challenge," Armstrong recalled in his authorized biography, "First Man" by historian James Hansen.

The spacesuit that Neil Armstrong wore for the Gemini 8 mission was based on the same type of pressure suit he wore flying the X-15 rocketplane four years earlier. His suit and helmet are today on display at the Armstrong Air & Space Museum in Wapakoneta, Ohio.

Neil Armstrong's Gemini 8 flight marked the first time a U.S. civilian flew into orbit. Armstrong had retired from the U.S. Navy in 1960.

The Gemini 8 mission was planned as a three-day mission but lasted just one day after a stuck thruster set the spacecraft spinning. To regain control, Armstrong had to use the re-entry system thrusters, which meant ending the flight early, forgoing a planned spacewalk.

After surviving the first critical in-space emergency for a U.S. spacecraft, Neil Armstrong and David Scott splashed down east of Okinawa and south of Yokosuka, Japan. The USS Leonard F. Mason recovered the crew and capsule three hours after they landed.

Two days after returning to Earth, Armstrong was assigned to backup his flight's backup crew, Charles Conrad and Richard Gordon, who were now prime to fly the Gemini 11 mission. His own next spaceflight would also be numbered "11," and would take him to the moon.

In addition to their roles flying the spacecraft, Apollo 11 moonwalkers Neil Armstrong (left) and Buzz Aldrin needed to become part-time geologists. Here, five months before their launch, Armstrong and Aldrin train during a geology field trip to Sierra Blanca in Texas.

The training prepared Armstrong and Aldrin to return the first geologic samples from the moon back to Earth. In all, the two collected 48.5 pounds (22 kilograms) of material, including 50 rocks, samples of the fine-grained lunar regolith (soil), and two core tubes that included material from up to 5.1 inches (13 centimeters) below the moon's surface.

Neil Armstrong, wearing an early training version of the Apollo spacesuit he would wear on the moon.