Just as the study of seismic waves lets us look into the bowels of the Earth, helioseismology has for more than 20 years been a rich source of information about the interior of the Sun. Apparently driven by internal convective motion, the Sun rings like a great spherical bell. Many thousands of resonant pressure‐wave modes with periods on the order of 5 minutes have been painstakingly decoded from complex surface motions of dauntingly small amplitude. From the pattern of resonant frequencies one learns much about the composition, density and structure of the Sun. We now know, for example, that the Sun's convection zone is twice as deep as solar modelers believed before these oscillation modes were measured.