Like many other stars and planets, the Earth and the Sun possess magnetic fields built by dynamo action. Unlike the magnetism of most other astrophysical objects, though, the Solar and terrestrial fields have been closely studied for generations, yielding a wide variety of observational constraints that continue to challenge theory and defy prediction. Both analytical theory and numerical simulations have cumulatively yielded significant insight into how both objects build their magnetism, but a comprehensive understanding of this process has remained elusive. This meeting will aim to scrutinise and assess the results of such modelling efforts by comparison to the vast and ongoing array of observations of both the Earth and the Sun.