2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/136991In order to understand the composition of planetary nebulae we first need to study the nucleosynthesis occurring in the progenitor star during the thermally-pulsing Asymptotic Giant Branch (AGB) phase. I present an overview of single AGB evolution, with an emphasis on the mixing processes that alter the envelope composition, followed by a discussion of the stellar yields available from single AGB stellar models.8 pages. To appear in "Asymmetrical Planetary Nebulae IV," eds. R. L. M. Corradi, A. Manchado & N. SokerAstrophysicstext