Thirteen facts that you need to know on multiple populations in globular
  clusters
  I review the methods, mostly developed in the last decade, that are commonly
used to identify and characterize multiple populations (MPs) in Globular
Clusters based on photometry. I summarize the results from the recent surveys
of MPs with the Hubble Space Telescope and ground-based facilities and provide
a list of the main properties of MPs as inferred from these studies.
