Here is my take. I think the need to have a 'birds and bees' talk when your kid hits the age of 10 is nuts. Then everyone is aware and embarrassed and there is no need for the Big Talk. We should be having the Big Talk all the time! My oldest just turned 4 and has asked me where babies come from. I think they are talking about it at pre-school. So I need to get in first, before he thinks they come from space ships or mom throws them up from her mouth because she's gotten too fat to keep them in anymore. Yep, those are some great preschooler stories! So I told him that Dad's start the process by putting the tiny seed in Mom and she grows the seed for nearly a year. He was fine with that and asked me how and where does the baby come out and I told him and he laughed hard, thinking it was a joke which made me laugh so I had to stop and get serious! So now he's ok with that too. Then a week later he asked "but HOW does that Dad put the seed in?" and I thought, oh God. Not that I have a problem telling him but he'll obsess about it. He is 4 and is well aware of his private parts and their 'other' function because all young children are sexually aware in a natural and very innocent kind of way. He knows that some behaviors belong in his room and that they are perfectly ok, but they are private. So honestly - the earlier the better. Let them know exactly where babies come from, in an age appropriate manner. The next time he asks HOW a Dad puts the seed in, I'll just tell him. I know he'll get a giggle out of it but as long as I act normally and don't make a big deal of it, he won't either. I still shower with all my children (goodness, you do? yes I do!) so they are very aware of different bodies and different parts and really could not care less. It's all pretty normal to them, although we'll stop showering with our oldest in the next few months, simply because we have to stop at some stage! So starting at age 3 is my recommendation and as long as it's done simply and respectfully, none of us will ever have to dread The Talk that shouldn't have to happen anyway.