Michael Phelps asked Katie Ledecky for an autograph - 10 years and countless gold medals since their introduction.
A photo of a nine-year-old Katie Ledecky posing awkwardly in an autograph session with Michael Phelps - by then well on his way to becoming the most decorated Olympian in history - went viral before the two went on to dominate in Rio.
Phelps asked Ledecky to return the favour.
Ledecky, now 19, shared that old picture juxtaposed with an updated version from Monday showing Phelps on the opposite side of the table waiting for her to sign his poster.
Ledecky and Phelps collected 11 medals between them in Rio - nine of them gold.
And as Phelps has declared these his final Games, this photo becomes emblematic of a passing of the torch in United States swimming.