I am a student of history and I write fanfiction for Doctor who as well as short stories. 
While studying history I realized how the course of the present and our reality could have changed if simple events and, or actions of individuals had altered slightly. What if? 
What if Columbus's ships had sunk during a storm?  What if John F. Kennedy had not been assassinated? What if Hitler had died from the poison gas attack that temporarily blinded him?  What if?