Reality TV star and former Olympic medallist Bruce Jenner's new look as a woman was unveiled on the cover of Vanity Fair this week.
On Monday, she revealed her new name as Caitlyn Jenner, and launched a Twitter account that attracted more than 1 million followers in four hours and three minutes, a new world record.
Who is Bruce and how did he become Caitlyn? Here's a quick look:
1. Olympic medallist
Born in 1949, Bruce Jenner had dyslexia and struggled in school. But he excelled in sports, and became an American sporting hero by setting a world record in the decathlon in the 1976 Olympics in Montreal. He was inducted into the Olympic Hall of Fame in 1986.
2. Actor, racer, et al
After the Olympics he was a spokesman for Wheaties breakfast cereal. He also acted in the television series The Love Boat, during the late 1970s and early 1980s. He was also a race car driver in the 1980s.
He is a motivational speaker, television sports commentator and author of several books.
3. Three marriages
He has six children from three marriages.
He was married to Chrystie Scott from 1972 to 1981, and they had a son, Burton, and a daughter, Cassandra.
Less than a week after his divorce was finalised, he married actress Linda Thompson. They have two sons, Brandon and Sam Brody, and divorced in 1986.
After five months of dating, he married Kris Kardashian in 1991. They have two daughters together, Kendall and Kylie. Kris has four children from her prior marriage - Kourtney, Kim, Khloe and Rob. Jenner and Kris recently divorced in 2014.
4. Reality TV star
Jenner once again became a household name with the reality TV series Keeping Up With The Kardashians, appearing as the sometimes bemused stepfather of the flamboyant Kardashian daughters.
As Caitlyn Jenner now, she will be getting her own show documenting her transition to a woman.
5. Coming out as transgender
Jenner has been the most high-profile American transgender to date. She made the announcement in an interview with ABC's Diane Sawyer in April.
What celebrities are tweeting about Caitlyn Jenner:
