The little boy runs up to his father and asks him, "Dad, what's 'sex'?"

His father was obviously more than a little taken aback up this question, but he figures to himself that if his 4 year old is old enough to ask it then he deserves a proper explanation.

So he seats him down next to him and gives him the whole deal - drawings, pictures from the Internet on his phone, etc.

Meanwhile, the son appears to be getting more and more confused. Finally, when the father thinks he's done, he stops and asks, "All right, my boy. Now, do you have any questions?"

The son shakes his head hesitantly, still a little taken aback by all that he's been told.

"Oh by the way," the father continues. "Where'd you hear the word from?"

The son replies, "Mom said that dinner would be ready in a coupla secs."