In: "Star Clusters: From the Milky Way to the Early
Universe", Proceedings IAU Symposium No. 351, 2019, A. Bragaglia,
M.B. Davies, A. Sills & E. Vesperini, eds.
https://arxiv.org/abs/1908.11703
Abstract: I review the methods, mostly developed in the last decade, that are commonly used to identify and characterize multiple populations (MPs) in Globular Clusters (GCs) based on photometry. I summarize the results from the recent surveys of MPs with the Hubble Space Telescope (HST ) and ground-based facilities and provide a list of the main properties of MPs as inferred from these studies.