  Since the first observations of solar oscillations, helioseismology has been
one of the most successful fields of astrophysics. Data of high quality were
obtained through the implementation of networks of ground-based observatories
such as the GONG project or the BiSON network, coupled with space-based
telescopes such as SOHO and SDO missions. Besides the improvement of
observational data, solar seismologists developed sophisticated techniques to
infer the internal structure of the Sun. These methods, then already
extensively used in the field of Geophysics, are called inversion techniques.
They allowed to determine the position of the solar convective envelope, its
helium abundance and the internal radial profiles of thermodynamic quantities.
Back in 1990s these comparisons showed a very high agreement between solar
models and the Sun. However, the downward revision of the CNO surface
abundances in the Sun induced a drastic reduction of this agreement leading to
the solar modelling problem. More than ten years later, in the era of the
space-based photometry missions which have established asteroseismology of
solar-like stars as a standard approach to obtain their masses, radii and ages,
the solar modelling problem still awaits a solution. We will present the
results of new helioseismic inversions, discuss the current uncertainties of
solar models as well as some possible solutions to the solar problem. We will
show how helioseismology can help us grasp what is amiss in our models. We will
also show that, far from being an argument about details of solar models, the
solar problem has significant implications for seismology of solar-like stars,
on the main sequence and beyond, impacting asteroseismology as a whole as well
as the fields requiring precise and accurate knowledge of stellar masses, radii
and ages, such as Galactic archaeology and exoplanetology.
