In pictures: Superstar gymnast Simone Biles

American gymnast Simone Biles is the defending Olympic champion in the individual all-around, and if the high-flying 24-year-old wins in Tokyo she will be the first woman to repeat since Vera Caslavska in 1968.

Many consider Biles to be the greatest gymnast of all time. Over the past few years, she has astounded us with never-before-seen moves; there are now four original skills that are named after her. And earlier this year she became the first woman to land the Yurchenko double pike vault in competition.

Biles suffered an early setback in Tokyo when she pulled out of the team competition over what she said were mental-health concerns. Biles stumbled on the vault, Team USA’s first apparatus of the day, before being replaced by Jordan Chiles.

Biles, who led Team USA to Olympic gold in 2016, later broke down in tears as she explained her decision to reporters.

“I have to focus on my mental health and not jeopardize my health and well-being,” she said after the competition.