The astronaut who thought he had grown 9cm!

Japanese astronaut Norishige Kanai thought he'd grown a whole 9cm since arriving at the International Space Station just over three weeks ago.

It sounded crazy! People around the world were fascinated, and started trying to work out how something like this could happen.

Norishige was even worried he wouldn't fit in his spacecraft to come back home again.

But instead, it turns out he'd just measured himself wrongly.

He had grown taller, but only by 2cm, which is normal for astronauts. Awkward!

So how did it happen? Ayshah has this...