From the advent of individualized carbon nanotubes nearly 20 years ago to the current ability to control their properties at multiple levels, the world of CNTs has changed tremendously. Through the lens of my group’s efforts, I will provide a retrospective on how our understanding of CNTs has changed through this period. An overview will be given of our efforts on Raman and photoluminescence (PL) spectroscopy to identify and characterize fundamental CNT properties. While spectroscopic separation enabled many revelations on CNT photophysics, the limitations imposed by mixed-chirality samples ultimately were overcome with the advent of effective and efficient methods for chirality enrichment. Examples will be given of advances in photophysics established through Raman performed on pure chirality samples. New separations techniques presented new questions on nanotube surface chemistry, ultimately leading to studies of surface chemistry, surface structure, and defects, at the ensemble and single tube levels. Most recently, development of functionalization methods to introduce optically active defect states has opened an exciting new direction in nanotube studies. An overview of the new photophyics and quantum light emission enabled by defects will be given, along with some perspective on future outlook.