When I started to make this episode, I thought I would try to do a comprehensive review of all of the various functions of serotonin across its 15 or more receptor types, but I soon found myself overwhelmed. More importantly, I found that some stories are more interesting to tell than others, so here I discuss serotonin and focus on how a few 5-HT receptors can not only help us survive, but also motivate ourselves to reach our goals, and, sometimes, convince us that we are fusing bodies...