The Sun is the only star that can be studied in detail. The last decade saw a revolution in the scope, amount, and the quality of solar data. Coordinated quantitative observations link the processes in the deep interior to those in the outer atmosphere. Numerical simulations and theoretical modelling have produced detailed agreement with observations. The most important lesson the Sun is now teaching us is that the parallel development of quantitative measurements with numerical simulation and theory can produce a physical understanding of the complex nonlinear phenomena that occur over a wide range in densities, pressures, temperatures and plasma betas. Understanding the physics of the Sun is a major key to unravelling puzzles throughout astrophysics.