How do you tell if a rodent is a male or female?

So maybe im just blind or stupid but i can't tell on mice or baby rats. Now of course adult male rats are easy to see the two bowling balls at the base of his tail. All the mice seem like they all have a little buldge and it doesnt differ from male to female. There obviously has to be a difference. If someone could post some pictures of the different sizes of rats and mice and there male and female parts id appreciate it.

You gotta lift the tails and compare two of them. The boys genitalia will be farther away from the anus than girl genitalia. You will eventually get two that look different, and start comparing with the boy. (i find its easier against a boy)

With rats, I give them a slight squeeze (around the bum) and the boys (thingys) pop out so thats how I tell... and they girls (thingy) doesn't! When they are adults you can tell just by looking at them... lol

Here check this out with baby's it can be hard to tell.

http://www.afrma.org/sexing101.htm

Here's a good one on sexing rats. Just remember whether it's rats or mice never try to sex by hanging the rodent head down by it's tail. Not only can that hurt the tail, it causes any developing testes to retreat back into the body cavity and defeats the whole purpose of seeing what's there to be seen.

http://www.ratz.co.uk/sexingrats.html