Six of the youngest ever sports stars
Norwegian footballer Martin Odergaard has hit the news by signing for Spanish giants Real Madrid aged just 16.
When he was 15 and 253 days old, Odergaard became the youngest player ever to play in a European Championship footy qualifier when he appeared for Norway.
But he's not the only one to take on the sporting world at a young age.
Here's our guide to some of the other youngest-ever sporting superstars.
The youngest on the list - US golfer Lucy Li became the youngest ever person to qualify for the US Women's Open.
Aged just 11, Li managed to win a spot in the 2014 competition.
She didn't manage to make it though to the second part of the event - but is definitely a name to look out for in the future.
Who? You may well ask - but Matthew Briggs is the youngest footballer ever to play in the Premier League.
Aged 16 years and 65 days, he came on as a substitute for Fulham in their match against Middlesbrough in 2007. A flexible defender, he now plays for Millwall in the Championship.
If you're a tennis player, winning Wimbledon is seen as the ultimate prize. It takes skill, courage, determination and an incredible will to win in the face of massive pressure.
So when 16-year-old Swiss star Martina Hingis won the women's single title in 1997, she became the youngest ever winner of the grass court Grand Slam. She'd already been crowned the youngest junior Wimbledon champion, aged 13 in 1994.
Arsenal superstar Theo is the youngest footballer ever to play for England, when he played against Hungary in May 2006.
Aged 17 years and 75 days, Walcott had never played in the Premier League and had only played 13 matches of senior football. He then went on to be picked in the England squad for that summer's World Cup in Germany.
Rugby is a tough, physical game in which you need to be big, strong and brave.
George Ford was all those things, even though he was only 16 years and 237 days when he became the youngest person to play professional rugby in England. He played for Leicester Tigers in 2009, and is now a big part of the England squad.
Imagine having an Olympic gold medal at just 15. Well that's what happened to Tara Lipinski, who is the youngest woman to ever win a Winter Olympic gold. The American figure skater took home the medal at the 1998 winter games in Nagano.