ELI5 Morning People - What makes someone a morning person?

What makes someone a morning person? How do you explain the Circadian clock? If I'm not one, is it possible to become a morning person?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: brylow, slingbladerunner, cjc09, auroun2013 & hansfredderik   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]