The space shuttle Endeavour has lifted off on its 25th and final mission.
"8, 7, 6, 5, 4, 3, 2, 1, 0 ... and liftoff for the final launch of Endeavour, expanding our knowledge and expanding our lives in space."
And, with that, six astronauts and the youngest shuttle in NASA's fleet, Endeavour, blasted off from the Kennedy Space Center in Florida, bound for the International Space Station.
Astronaut Mark Kelly is commanding Endeavour's final mission.
He shared a few words with mission control about 10 minutes before launch.
"As Americans, we endeavor to build a better life than the generation before, and we endeavor to be a united nation," said Kelly. "In these efforts, we are often tested. This mission represents the power of teamwork, commitment and exploration. It is in the DNA of our great country to reach for the stars and explore. We must not stop."
Kelly's wife, U.S. Congresswoman Gabrielle Giffords, attended Monday's launch. Giffords was severely wounded during a shooting rampage in Arizona in January and has been recovering at a medical center in Houston, Texas.
She was among the estimated half-million spectators at the liftoff.
Endeavour was set to launch in late April, but an electrical problem in a heater circuit forced a delay. Engineers replaced the switchbox and installed new wiring.
A few hours ahead of Monday's launch, technicians repaired damage to tile around the shuttle's crew hatch, but NASA said it would cause no issue for the flight.
After the successful liftoff, Shuttle Launch Director Mike Leinbach spoke to reporters.
"Endeavour is in orbit safely and is going to perform a great mission, and we'll see her back here on June 1," he said. "So, a great day here at the Kennedy Space Center and for the shuttle program."
The primary objective of Endeavour's 16-day mission is to deliver the Alpha Magnetic Spectrometer to the International Space Station. The spectrometer, or AMS, is a sophisticated detector that will help researchers study the formation of the universe.
It will look for elusive evidence of anti-matter by searching for anti-carbon and anti-helium molecules among all discernible particles.
This will be the last mission for Endeavour, and the second-to-last mission for the U.S. shuttle fleet. NASA is retiring the shuttles in order to focus on developing the next generation of spacecraft that could go beyond low-Earth-orbit.
The next and final launch of the space shuttle Atlantis is set for July.