One of the most fascinating things about this topic is the fact that it is almost never discussed in the community despite it being a primitive that is deeply involved in Enumerators! I became fascinated with this topic when I wanted to performance optimize Ruby for standard technical interview questions, like FizzBuzz and Fibonacci. I discovered that using Enumerator.new and then defining a basic Fibonacci was far quicker than defining a Fibonacci method with the same logic, and soon found that this was due in part to the concurrency built into Enumerators stemming from Fiber. The fact that this primitive is so incredibly engrained in Enumerators (which Rubyists use in virtually every project!) and yet has so little discussion surrounding it makes it the perfect topic to teach developers both old and young something interesting that they weren't aware of before. Understanding Fibers will help developers better understand Ruby better as a language, but also is another tool to add to their repertoire that is simultaneously esoteric and valuable, an exceedingly rare combination.