In the 3rd millennium BCE, Mesopotamian kings recorded and interpreted their dreams on wax tablets. In the years since, we haven't paused in our quest to understand why we dream. And while we still don't have any definitive answers, we have some theories. Amy Adkins reveals the top seven reasons why we might dream. [Directed by Claire Van Ryzin, Chris Anne Lindo and Sam Lee, narrated by Addison Anderson].