Where do babies come from joke

On the way back from a Cub Scout meeting, my grandson innocently said to my son, “Dad, I know babies come from mommies” tummies, but how do they get there in the first place?”

After my son hemmed and hawed awhile, my grandson finally spoke up in disgust, “You don”t have to make up something, Dad. It’s okay if you don’t know the answer.”