Scientists have found out more about why some people are left-handed.
About one in 10 people is left-handed and it's never really been understood why people use that hand over their right.
But scientists at the University of Oxford say it could be down to genetics - after finding the first genes linked to being left-handed.
The genes are hardwired, or permanently connected, into human DNA and found in a part of the brain that deals with language.
One of the researchers told the BBC: "It tells us for the first time that handedness has a genetic component."
But there are still many mysteries when it comes to the connection between brain development and which hand you use.
Famous lefties include former President of the United States Barack Obama, the Duke of Cambridge, singers Niall Horan and Justin Bieber and Little Mix's Jesy Nelson.
Are you left-handed? Let us know in the comments!