First we will discuss which are the the uncertainties in neutron star (NS) radii and crust properties due to our limited knowledge of the equation of state (EOS) and demonstrate the importance of a unified microscopic description for the different baryonic densities of the star. We will next present the effect of strong magnetic fields, of the order of 10^15-10^17 G, on the extension of the crust of magnetized neutron stars from the analysis of the dynamical instability region of neutron-proton-electron (npe) matter at subsaturation densities. It is shown that the effect of a strong magnetic field on the instability region is very sensitive to the density dependence of the symmetry energy, and that it originates an increase of the extension of the crust and of the charge content of clusters.