  Planetary nebulae retain the signature of the nucleosynthesis and mixing
events that occurred during the previous AGB phase. Observational signatures
complement observations of AGB and post-AGB stars and their binary companions.
The abundances of the elements heavier than iron such as Kr and Xe in planetary
nebulae can be used to complement abundances of Sr/Y/Zr and Ba/La/Ce in AGB
stars, respectively, to determine the operation of the slow neutron-capture
process (the s process) in AGB stars. Additionally, observations of the Rb
abundance in Type I planetary nebulae may allow us to infer the initial mass of
the central star. Several noble gas components present in meteoritic stardust
silicon carbide (SiC) grains are associated with implantation into the dust
grains in the high-energy environment connected to the fast winds from the
central stars during the planetary nebulae phase.
