Planetary nebulae as probes of the chemical impact of AGB stars
  Planetary nebulae (PN) represent the evolutionary fate of the asymptotic giant branch (AGB) stellar envelopes, thus are ideally suited to study the chemical impact of AGB stars. Stellar evolution predict elemental enrichment through the AGB evolution, and convective dredge-up episodes allow the products of stellar evolution to reach the stellar outer layers. Planetary nebulae are probes of these processes, and are also probes of the environment at the time of formation of their progenitors, through the elements not affected by AGB evolution. Ultimately PN may be used to test AGB stars as actors and probes. Planetary nebulae are easily identified and detected in the galaxy, the Magellanic Clouds, and beyond, thus they are probes of AGB evolution an stellar populations in different environments as well. 
Letizia Stanghellini