Jack: Waaaait, is that true?!
me: Sort of. All babies start with 2 X chromosomes for girls. The boy Y chromosome kicks in later.
Jack: What are you talking about?
me: Babies start as girls and then switch to boys if they’re supposed to.
Jack: There is gonna be a riot in my school when I tell my friends!!
me: Don’t go crazy, okay?
Jack: Hey! Is that why boys have nipples???