Globular clusters: near but still mysterious

Globular clusters are among the most interesting objects in our Galaxy: they are the oldest bodies, whose age determination can put constraints on the age of the Universe, they trace important phases of the early evolution of the Galaxy, and they are important laboratories for stellar evolution and stellar dynamics.
Even if globular clusters are relatively near to us, the determination of their age and evolutionary history are still affected by several uncertainties. Moreover, in recent years accurate photometric and spectroscopic observations have provided sound evidence that Galactic Globular Clusters can not be longer considered the prototype of Simple Stellar Populations.