Signatures of stellar depletion on the Spite plateau

The predicted primordial lithium abundance is about three times higher than the Li abundance inferred from spectroscopic observations of metal-poor stars on the Spite plateau. This cosmological problem could be explained either by exciting new physics or by stellar depletion during the pre-main sequence and/or the main sequence. We discuss the Li abundance pattern in different stellar populations, showing that the Spite plateau is 'universal', meaning that the Li problem is present in distinct Galactic and extra-galactic populations. We discuss high precision and homogeneous studies of large sample of stars, covering different stellar masses and metallicities. Clear atomic diffusion signatures are observed in globular clusters, indicating important stellar Li depletion. Among main sequence field stars, there is a significant decrease of lithium abundances for both lower effective temperatures and lower stellar masses, suggesting that stellar depletion is the cause of the cosmological lithium problem.