Mle mice or a female mice

Question
I bought 4 mice. and i don't know which are male and which are females. How do you tell them apart?

Answer
Hi,

Sexing mice is relatively easy. All you need to do is check under their tummies - if you see nipples you're holding a girl, and if not, it's a boy. Males also have rather large testicles under their tail - they 'hide' them when they're being cautious, but after a few minutes on your hand they should be relaxed enough to reveal them.