After more than 50 years since the first measurements, the study of e+e annihilation processes at low energies are still a great source of information in an energy region where perturbative Quantum Chromodinamyc cannot be used.

In particular, the hadronic cross section ia the experimental input for the theoretical calculation of the hadronic contribution to the anomalous magnetic moment of the muon, allowing for precise tests of the Standard Model and searches for New Physics effects. Thanks to the high luminosity of the B-factory PEP-II, the BaBar Collaboration has performed a number of precise measurements of e+e- -> hadrons processes over a large energy range. The measurements use a method pioneered by BaBar, based on the Initial State Radiation, which effectively lower the center-of-mass energy of the collision.

We present here the main results obtained on the measurement of exclusive cross sections for a variety of multi-hadronic final states, discussing in particular the implications for the muon g-2.