Disentangling multiple stellar populations in globular clusters using
  the Str\"omgren system
  An increasing amount of spectroscopic and photometric evidence is showing
that the stellar populations of globular clusters are not as simple as they
have been considered for many years. The presence of at least two different
populations of stars is being discovered in a growing number of globular
clusters, both in our Galaxy and in others. We have started a series of
observations of Galactic globular clusters using the Str\"omgren photometric
system in order to find the signatures of these multiple populations and
establish their presence in a more complete sample of globular clusters in the
Milky Way, and to study their radial distributions and extensions. We present
here the first results of our survey.
