An increasing number of observations over the last years have shown the existence of distinct sub-populations in many (maybe all) globular clusters and shattered the paradigm of globulars hosting single, simple stellar populations. These multiple populations manifest themselves in a split of different evolutionary sequences in the cluster color-magnitude diagrams. Using filters covering an appropriate range of wavelengths, photometry splits the main sequence into two or more branches, and in many cases this bimodality is repeated in the subgiant and red giant regions, and on the horizontal branch. In this talk I will summarize the main results from photometric studies.