Scientists think they have discovered why some people sleepwalk.
Sleepwalking affects lots of people - especially kids - and often involves getting out of bed and going for a wander while asleep.
Experts reckon sleepwalkers get it from their parents - and it's passed down through families.
If you are sleepwalker it's in your DNA - that's the complicated code that makes us special and who we are before we are born.
We get our DNA from our parents - and a study on sleepwalking has revealed if your parents sleepwalk - there's more chance you will.
About one out of 10 kids experience sleepwalking - it's more likely to happen when someone is really tired, and usually happens soon after they have fallen asleep.
It can happen in lots of different ways - from just sitting up in bed, to people leaving the house.
Sleepwalking usually last a few minutes after which the walker will usually get back into bed!