  Analysis of high-resolution stellar spectra relies heavily upon atomic data.
These include energy levels, wavelengths, cross-sections for various types of
interactions between particles and photons, such as photoionization and
collision induced transitions. Quantum-mechanical calculations provide largest
part of these data. In this paper I describe atomic data necessary to compute
model atmospheres and line formation for the late-type stars both in the
assumption of local thermodynamic equilibrium (LTE) and in a more general case
of non-LTE. I will focus on transition metals with 21 < Z < 29 and discuss
whether (and where) more complete and/or accurate atomic data are necessary.
