  Understanding how cool stars produce magnetic fields within their interiors
is crucial for predicting the impact of such fields, such as the activity cycle
of the Sun. In this respect, studying fully convective stars enables us to
investigate the role of convective zones in magnetic field generation. We
produced a magnetic map of a rapidly rotating, very-low-mass, fully convective
dwarf through tomographic imaging from time series of spectropolarimetric data.
Our results, which demonstrate that fully convective stars are able to trigger
axisymmetric large-scale poloidal fields without differential rotation,
challenge existing theoretical models of field generation in cool stars.
