UPDATE: Space Shuttle Endeavour launched on Monday May 16, jut before 9 a.m.
NASA delayed the mission from April 29 because of mechanical difficulties.
This marks Endeavour's last voyage into space and the next-to-last space shuttle mission.
Since Endeavour's first flight in 1992, NASA has released some unforgettable photos from the shuttle's history. Join us as we take a look back at daring spacewalks, picturesque launches and showstopping views from orbit.
Vote for the most iconic images and check on our live stream of the shuttle's 25th and final launch (April 29, 3:37 p.m. EDT).
For more memories from retired space shuttles, take a look through the best photographs from Space Shuttle Discovery's history.