  In addition to study extragalactic stellar populations in their integrated
light, the detailed analysis of individual resolved objects has become
feasible, mainly for luminous giant stars and for extragalactic planetary
nebulae (XPNe) in nearby galaxies. A recently started project at the
Astrophysical Institute Potsdam (AIP), called ``XPN--Physics'', aims to verify
if XPNe are useful probes to measure the chemical abundances of their parent
stellar population. The project involves theoretical and observational work
packages.
