In Japan, where more people run marathons than anywhere else, it takes a special character to stand out from the crowd.

By studying the movement of runners at the start of marathons, researchers have just shown that the collective movements of these crowds can be described as liquid flows. The flows observed before a 2016 race in Chicago subsequently helped predict those of thousands of runners in the starting corral of the 2017 Paris marathon.

Country superstar Shania Twain shares with Savannah Guthrie her favorite concert experience, what music does for her and more on "Six-Minute Marathon With Savannah."