  Convection is the most important physical process that determines the
structure of the envelopes of cool stars. It influences the surface radiation
flux and the shape of observed spectral line profiles and is responsible for
both generating and damping solar-like oscillations, among others. 3D numerical
simulations of stellar surface convection have developed into a powerful tool
to model and analyse the physical mechanisms operating at the surface of cool
stars. This review discusses the main principles of 3D stellar atmospheres used
for such applications. The requirements from stellar structure and evolution
theory to use them as boundary conditions are analysed as well as the
capabilities of using helio- and asteroseismology to reduce modelling
uncertainties and probing the consistency and accuracy of 3D stellar
atmospheres as part of this process. Simulations for the solar surface made by
different teams are compared and some issues concerning the uncertainties of
this modelling approach are discussed.
