Betelgeuse’s “Great Dimming” in the winter of 2019-2020 quickly became a source of fascination for both professional and amateur astronomers. Drastic enough to be easily detected with the naked eye, the star’s drop in brightness was unprecedented in observational memory and revealed the extent to which the workings of red supergiants are still a mystery. As the coldest and physically-largest members of the massive star population, red supergiants are ideal sources for studying the extremes of stellar physics and a key turning point in the evolution of post-main-sequence massive stars. They are also core-collapse progenitors and a crucial step in the formation of compact object binaries and multi-messenger mergers. Using Betelgeuse and its recent behavior as an archetype, this talk will survey our current knowledge of red supergiants and identify some of the most pressing open questions about these stars. It will also explore the evolving world of observational astronomy and the wealth of possibilities facing us in the coming decade as we study massive stars with a new generation of telescopes.