Where does a baby come from?

Yesterday, as we were travelling to go for a hike up at Mt. Spokane, Ruby was pondering in the back seat.  She piped up and asked me, "Mom, does a baby just appear in your tummy?"  I said, "No, a husband and wife have to make a baby!"  She then said, "How?"  I was a little stunned, but decided to tell her, "A mommy and daddy make a baby with love!"  I was thinking she would keep asking more specific questions, but this answer seemed to satisify her curiosity.  You could see the wheels spinning in her head, but she accepted it and moved on to other things.  Whew.....she is so inquisitive, I am sure we will be discussing the birds and bees in no time!