Sophie discusses fear and explains its purpose: to keep us alive. She illustrates what happens to our bodies when we're scared and mentions the different ways in which fear can be evoked. She then talks about the flight or flight response and references Charles Darwin's "Flinch" experiment that he conducted on himself.

Beakman explains earwax and its purpose using a giant ear with wax in it and an animated clip. He also explains why your ears pop due to the change in pressure.

Sophie conducts an experiment in which she creates a snot-like substance. She then explains the purpose of snot and provides a fun fact: we have mucus in our eyes.

Aunt Cass begins to stress eat after picking up Tadashi and Hiro from the police station.

Beakman explains flatulence and why our bodies build up gas that needs to be expelled. He explains how various foods affect the bacteria in the colon and that they release gas and cause it to accumulate. They also mention that the sound of flatulence comes from the anal sphincter.