Hey,
I was wondering when baby mice can leave their parents.. My friends mouse has had babies and I am taking one of them home with me sometime in the near future. I have owned mice all my life but this is the first time I will have ever had a YOUNG mouse... Their eyes are open (have been for around 3 or 4 days) and they do have fur. I was also wondering how you tell a YOUng mice's sex.. I do not want a male is why I am asking..

Mice are usually weaned at about 15- 21 days after birth. As with other animals, it's best to leave them with mama as long as possible, so I generally separated them at around 21 days.

Sexing baby mice is pretty hard sometimes. Describing it in text is even more difficult, but the best advice I can give is this: The distance between the anal opening and the genital opening is closer on females and farther apart on males.

I found a website with pretty good photos to help you visually:
http://www.thefunmouse.com/info/sexing.cfm