"In you go" is used as an informal, polite request for someone to enter something (walk through a door, enter a house, etc.), especially when the person did not enter at the appropriate time. It is often used with children, and sometimes simply to narrate what is happening for infants/toddlers. For example: 1. A father says to his small child: "let's get in the car." 2. The child is distracted by something on the ground, so the father walks over and guides the child into the car. As he does this, he says "in you go."

"In you go" is used as an informal, polite request for someone to enter something (walk through a door, enter a house, etc.), especially when the person did not enter at the appropriate time. It is often used with children, and sometimes simply to narrate what is happening for infants/toddlers. For example: 1. A father says to his small child: "let's get in the car." 2. The child is distracted by something on the ground, so the father walks over and guides the child into the car. As he does this, he says "in you go."

It's a polite request (or order) Actually, it's a little bit patronising, you would probably use it mostly with children. It's a pretty idiomatic phrase, so there is no 'rule' as such. There are a few similar expressions:, you could say: Out you go Up you go Down you go. Through you go. ____ You could also say "in I go" / "in he goes" etc. This means "i'm going in" / "He's going in" etc