Astronauts prepare for final space missions
The US space shuttle Atlantis will blast off on what Nasa reckons will be its last ever mission before it the space ship retires.
If everything goes to plan, the rocket will launch from the Kennedy Space Center in Florida at 6.20pm UK time.
Police are expecting massive crowds on the road leading to the space centre.
The mission is to get a Russian piece of equipment - along with some batteries -to the International Space Station.
There are six astronauts heading into space, and they've said they know how important a piece of history they are involved in, but that they have to concentrate on the job in hand.
Sonali's amazing space experience
The commander said: "This is the kind of thing that's going to hit all of us after the mission, when we realise what part in history we played.
"I think the space shuttle is the single most incredible machine humanity has ever built."
Atlantis has flown 31 times and has travelled a whopping 186,315,249 km - that means it's been around the earth 4,462 times!
Future trips to space
The US shuttle Atlantis is about to go on its last ever mission into space.
US President Barack Obama has announced a new exploration policy that would take humans beyond the International Space Station (ISS), beyond the Moon and to Mars.