Star formation histories of resolved galaxies
  The colour-magnitude diagrams of resolved stellar populations are the best
tool to study the star formation histories of the host galactic regions. In
this review the method to derive star formation histories by means of synthetic
colour-magnitude diagrams is briefly outlined, and the results of its
application to resolved galaxies of various morphological types are summarized.
It is shown that all the galaxies studied so far were already forming stars at
the lookback time reached by the observational data, independently of
morphological type and metallicity. Early-type galaxies have formed stars
predominantly, but in several cases not exclusively, at the earliest epochs.
All the other galaxies appear to have experienced rather continuous star
formation activities throughout their lifetimes, although with significant rate
variations and, sometimes, short quiescent phases.
