The SLS rocket will power NASA's Artemis I moon mission, set for launch later this year.
The core stage of the SLS moon rocket sits between the twin boosters.
The Space Launch System is the most powerful rocket NASA has ever built, and it's meant to launch spacecraft and astronauts to the moon as part of the Artemis program.
While NASA is still aiming to take humans back to the moon, this particular SLS is meant for Artemis I, an uncrewed mission around the moon that could launch later this year.
The core stage and boosters are now on the mobile launcher platform, a large support structure that can be moved (slowly) out to the launch pad when it's ready for takeoff. .