When I was about 6, my mother read me a book that explained to children how babies are made.
At about age 10, my mom gave me a book called "What's Happening to Me?". It was a bunch of cartoon drawings that explain what happens to your body through puberty to adulthood.
She asked me if I had any questions but I was too embarrassed to say anything. I don't think we had an actual sex talk until I was much older and it was more of, "Mom, the school is increasing the price of my birth control pills. Can I put them under our prescription insurance?" I proceeded to get a lecture on using proper protection.
ETA: I just had to add a pic of the book she gave me because it cracks me up.
