Felix Baumgartner is about to undertake if not the riskiest, then certainly the biggest, quite literally, jump in the history of mankind. He's jumping from the largest hot air balloon ever built from the edge of space with nothing but a special suite, a breathing apparatus and a carefully designed plan to help him.
He's about to set the world record for highest freefall jump, plunging from a height of 120,000 feet or 36,500 meters.
His freefall will last only a few minutes, but, because of the height and the incredibly thin atmosphere at that height, he'll accelerate to supersonic speeds.
He will thus become the first man to go supersonic without being flown by a plane, pushed by a spaceship or driven by a record-breaking car.
It won't take long for him to go supersonic, assuming everything goes well, he should reach 690 mph or 1,110km/h after the first 40 seconds.
He'll drop through most of the 36.5 km in the first few tens of seconds, but the entire jump, including the parachute ride, is expected to last about 10 minutes.
Three years of preparations for the Red Bull Stratos team will come down to this. But he's going to have to ascent for two and a half hours to reach the altitude needed in the balloon, before he can jump.
The jump is more than just a stunt, the type of which Felix Baumgartner is famous for, it will also be an opportunity to test new equipment and test what happens to the human body when falling from that height and reaching supersonic speeds.
NASA is especially interested in the data the jump may reveal for high-altitude bailouts. What's more, Baumgartner will be wearing a specially designed full-pressure suit, similar to the one worn by astronauts. But it's actually an upgrade in one crucial aspect, maneuverability.
Current astronaut full-pressure suits are designed for sitting around in a cabin. If something goes wrong at high altitude, there's no hope for them moving around and bailing out of the spacecraft.
Baumgartner's has to be maneuverable though to make it possible for him to jump out of the balloon and adjust his position in flight.
He'll also have to turn around completely during his jump. He'll jump feet first and fall straight for a while but he'll have to move to the more regular, head-down position for much of the freefall. If the suit performs well, the design could eventually be worn by actual astronauts.
The jump is scheduled to take place in a few hours, you can read more about it and the YouTube live feed here