What I think is pretty cool is that a single base change- so a one letter change in your DNA- can determine what ear wax you have. To put that into context- one copy of your DNA (genome) is 3 billion letters- so one change in 3 billion can determine what ear wax you have. Everyone actually has 2 copies of DNA in their cells so another way to put it is comparing the size of a genome to the worlds population. In this scenario comparison, your ear wax would be like replacing one person to another out of everyone that lives on earth!
This being said, it’s not so much the idea of earwax itself but rather-making an easy and cheap method that students can do to demonstrate how you could go about finding something in your DNA that results in a physical change in the body. The beauty of this experiment is that you can directly confirm the results by shoving your finger in your ear and seeing what ear wax you have!