Globular clusters: a chemical roadmap between anomalies and homogeneity
  For several decades, globular clusters have been considered the best example
of simple stellar populations, hosting coeval and chemical homogeneous stars.
The last decade of spectroscopic and photometric studies has revealed a more
complex view of their chemical composition, with a high level of homogeneity in
their iron content but star-to-star variations in some light elements. This
contribution summarizes the main evidence about the chemical anomalies in the
stellar content of the globular clusters, discussing also some peculiar objects
with intrinsic dispersions in their iron content.
