Eliud Kipchoge ran a marathon in 2 hours and 25 seconds on Saturday.
He was 26 seconds from making history as the first person to run a marathon in less than two hours.
What happened?
The Kenyan athlete competed in the Breaking2 project at the Monza Formula One track in Italy.
He completed 17.5 laps around the 1.5-mile track, smashing Dennis Kimetto's world mark by 2.5 minutes.
Why it matters for Eliud Kipchoge
Kipchoge's time didn't go down as an official world record due to variables like pacers entering mid-race.
He still broke his personal best time of 2:03:05, which was set at the London Marathon last year.
What comes next?
The 32-year-old continued in his trademark relaxed style and passed the halfway mark in 59:54.
He would have needed an average of less than 4:35 per mile to break the 2-hour barrier.
Eliud Kipchoge was happy with his performance, saying "I am happy that I've reduced by 2 1/2 minutes the world record."
He also stated that this attempt was not the end of the pursuit of a sub-2 hour marathon.
The Monza track was selected after extensive research that included average temperature, air pressure, and wind levels.
Two-time Boston Marathon winner Lelisa Desisa and Eritrean half-marathon world-record holder Zersenay Tadese also participated.
Nike CEO Mark Parker said, "Today, millions of people around the world watched as running history was written."
He praised Eliud Kipchoge's achievement, saying it was a moment of global inspiration that would encourage athletes to push their limits.
Kipchoge's time was initially listed as a second faster, then changed to 25 seconds off the 2-hour mark.
He finished the marathon with a time of 2:00:25, raising hopes that one of world sport's most famous barriers can be broken.
The Breaking2 project was held on the 63rd anniversary of Roger Bannister breaking the four-minute mile in 1954.
Eliud Kipchoge's attempt was widely followed, with many considering him the best marathon runner in the world.