Holly A. Shiels discusses the A.P. Farrell and D.R. Jones chapter “The Heart” in Fish Physiology, Volume 12A, published in 1992. The next chapter in this volume is the re-published version of that chapter. “The Heart” remains the greatest collection of comparative information on the anatomical, morphological, and physiological properties of the fish heart. It is a work of depth and breath, and a lesson in how the comparative approach provides physiological insight beyond the boundaries of the knowledge base from which it is generated. My introduction focuses on key areas from this chapter that are dear to my own heart including structure-function relationships, cardiac remodeling and regulation of heart function in an era of climate change. However, countless introductions could flow from Farrell and Jones' chapter as it touches on nearly every aspect of fish cardiac physiology. I very much enjoyed re-reading this chapter and recognizing its impact on my work. I hope the re-release of this chapter engages the next generation the way it did mine.