Atomic diffusion in stars is efficient in changing the distribution of elements slowly but strongly in any radiative zone. The process may produce detectable effects, over time-scales stretching from a few decades to star's lifetime, according to the depth of the radiative zones. The main consequences are that superficial abundances may depart from standard values, but also that internal structure and seismic diagnostics are affected owing to changes in local opacities. The main difficulty of including atomic diffusion in numerical models comes from radiation force (the dominant force acting on atoms within the layers concerned), which is specific to chemical species through their atomic properties, and which makes the process of abundance stratification strongly non-linear in usual situations (especially in atmospheres). This talk presented recent improvements that involve a fast method for calculating radiative accelerations in stellar interiors, and described progress in the modelling of stellar atmospheres.