AGB and post-AGB stars as VLTI targets

Low and intermediate mass stars turn into cool giants after their evolution on the main sequence. During these evolutionary stages, their surface is enriched in several chemical species. These stars are also characterized by large mass-loss rates revealed by their molecules and dust-rich circumstellar envelopes. They thus play an important role in the chemical evolution of the Universe. We present two examples of possible observations with the Very Large Telescope Interferometer of these evolved giant stars that could strongly contribute to our understanding of their properties and evolution: (i) detection of possible lithium abundance heterogeneities for asymptotic Giant Branch stars and (ii) observations of the dusty environment of R Coronae Borealis variables.