Explore the principles and applications of clumped isotope geochemistry in this 29-minute AGU conference talk. Delve into the classic problems of isotope geochemistry and discover how clumping in carbonates provides a solution. Examine the reaction mechanisms, temperature dependence, and historical context of this technique. Learn about similar geothermometers and understand the limitations of clumped isotope analysis. Gain insights into the methodology, power, and modern applications of carbonate clumped isotopes, including their use in Phanerozoic temperature reconstructions. Discuss the challenges faced in the field over the past 13 years and explore future directions in clumped isotope geochemistry research.