History beckons for the European Space Agency on Wednesday as it attempts to put a small probe on a comet.
Previous missions have flown by these "ice mountains" but no-one has ever emplaced a surface lander before.
Esa's Rosetta satellite will drop the probe on to Comet 67P/Churyumov-Gerasimenko from an altitude of 20km.
If all goes to plan, the little robot, called Philae, will touch down about seven hours later, deploying screws and harpoons to secure its position.
Confirmation is expected at Earth around 1600 GMT.
The first thing Philae will do on landing is send back a picture of its surroundings - a strange landscape containing deep pits and tall ice spires.
This is, though, an event with a highly uncertain outcome.
Science is awesome!