Atomic and molecular data for stellar physics: Former successes and future challenges

This review highlights current (and future) hot topics in astrophysics where atomic or molecular input data are (or will be) essential, with special emphasis on topics relating to nucleosynthesis and cosmochemistry. We first discuss issues (like the abundances of oxygen and iron in the Sun, and that of lithium in post-AGB stars) where the use of poor-quality atomic or molecular data have led to spurious astrophysical puzzles which sparked fancy astrophysical models or theories. We then address issues where the advent of new instruments (like the ultraviolet high-resolution spectrographs - GHRS onboard HST, Keck-HRS or VLT-UVES - or future infrared satellites) calls for new and accurate atomic or molecular data.