First things first, I'm not a parent, I'm 21f and I'm here for my sister. My father died 5 years ago and with me and my brother both being adults by that time my mother was left with my little sister. She's now 10, in the fourth grade, and is nearing puberty fast. I volunteered to have the talk with her, and being her big sister I figure it'll be more fun for her that way (mom is "boring"). Honestly I'm feeling pretty confident about this, she's mature for her age and easy to talk to. The only problem I'm having is where to draw the line between "period talk" and "sex talk". My mother and I agree that she's a bit young for the full on sex talk, but I'm unsure where to draw the line. I obviously want her to understand biologically why menstruation is a thing to begin with, which brings us to pregnancy, but where do I stop? I don't want to confuse her by bringing pregnancy and childbirth into the picture if I can't explain to her where babies come from yet. Any advice would be helpful, thank you.