Magnetic fields below, on and above the solar surface

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. Coordina ted quantitative observations link the processes in the deep interior to th ose in the outer atmosphere. Numerical simulations and theoretical modellin g have produced detailed agreement with observations. The most important le sson the Sun is now teaching us is that the parallel development of quantit ative measurements with numerical simulation and theory can produce a physi cal understanding of the complex nonlinear phenomena that occur over a wide range in densities, pressures, temperatures and plasma betas. Understandin g the physics of the Sun is a major key to unravelling puzzles throughout a strophysics.