  An increasing number of photometric observations of multiple stellar
populations in Galactic globular clusters is seriously challenging the paradigm
of GCs hosting single, simple stellar populations. These multiple populations
manifest themselves in a split of different evolutionary sequences as observed
in the cluster color-magnitude diagrams. Multiple stellar populations have been
identified in Galactic and Magellanic Cloud clusters. In this paper we will
summarize the observational scenario.

Solar and Stellar Astrophysics;Astrophysics of Galaxies