AGB stars and the chemical evolution of galaxies

Asymptotic Giant Branch (AGB) stars are important players in the chemical evolution modelling of galaxies, because they are major producers of several chemical elements and excellent tracers of the structure and of the star formation activity of their parent galaxies. A few examples on the importance of AGB stars are presented in this review, together with a number of open problems affecting chemical evolution model predictions related to the element enrichment by AGB stars: the evolution of $^4$He and Na in globular clusters, the evolution of $^3$He and the carbon isotopes in the Galactic disk, and the evolution of N and O in different types of galaxies. The need of homogeneous and complete sets of yields is emphasized.