Explore critical phenomena through the lens of the Ising model in this Green Family Lecture presented by Hugo Duminil-Copin from the University of Geneva. Delve into the rich mathematical history and theoretical applications of the Ising model, initially conceived for ferromagnetism but now recognized as a powerful tool for understanding cooperative phenomena. Examine the model's critical phase, including breakthroughs in two-dimensional and high-dimensional cases through integrability and mean-field behavior. Discover recent progress in the mysterious three- and four-dimensional cases, focusing on a probabilistic interpretation that connects the Ising model to percolation models. Gain insights into this fundamental lattice model of statistical physics and its significance in understanding phase transitions.