  The correct interpretation of the large amount of complex data from
next-generation (in particular, space-based) observational facilities requires
a very strong theoretical underpinning. One can thus predict that in the near
future the use of atmospheric models obtained through the use of
three-dimensional (3-D) radiation magnetohydrodynamics (RMHD) codes, coupled
with advanced radiative transfer treatment including non-local thermodynamic
equilibrium (non-LTE) effects and polarisation, will become the norm. In
particular, stellar brightness variability in cool (i. e., spectral type F, G,
K, and M) stars can be induced by several different effects, besides pulsation.
We briefly discuss some literature results and mention some of our recent
progress. Finally, we attempt to peek into the future of understanding this
important aspect of the life of stars.
