I will review our recent efforts to scrutinize the importance of diffusive processes in altering the chemical composition of long-lived solar-type stars. By analysing evolved and unevolved stars in a nearby globular cluster, we were able to show for the first time that there are atmospheric trends of abundance with evolutionary stage, in quantitative agreement with the most recent diffusion models. This finding has implications for early cosmochemistry and stellar age determinations. Moreover, it helps to understand why the amount of lithium in the atmospheres of old stars is seemingly lower than that known to be produced in the Big Bang.