Explore the fascinating journey of geometry from its classical origins to its pivotal role in modern physics in this Royal Institution lecture. Delve into the five axioms of Euclidean geometry and discover how post-Euclidean geometry revolutionized our understanding of spacetime. Follow the historical progression through the Renaissance and Enlightenment, learning how mathematicians like Gauss and Riemann challenged traditional axioms, ultimately paving the way for Einstein's theory of relativity. Gain insights into the connections between mathematics and physics, from ancient proofs to the principles of special relativity, as presented by Professor Yang-Hui He in this comprehensive exploration of geometry's impact on our understanding of the universe.