American Nik Wallenda is set to cross the Niagara Falls on a tightrope later today.
Making the trip unharnessed as he walks across a 5cm diameter cable, Wallenda can count seven generations of acrobats in the family
It'll take him over 30 minutes to make the 550m long crossing. The water will flow 60 metres beneath him. If he falls, he must grab hold of the cable or he will surely drown.
The trip will be the first attempt of its kind in 100 years.