Marco Ajello, SLAC/KIPAC
Fermi-LAT, with its unprecedented sensitivity, detected over a thousand point-like sources during its first year of operations. Being most of them blazars, the study of their population with Fermi-LAT represents a real breakthrough in the understanding of their nature. In this talk, the main features of the sample of blazars detected by Fermi will be reviewed focusing in particular on their statistical properties. We will present the logN-logS distributions of the entire blazar class and separately the one for BL Lac objects and FSRQs. Their contribution to the extragalactic background emission, as measured by LAT, will be evaluated. We will also discuss the cosmological evolution of FSRQs and BL Lac objects in the context of growth of super-massive black holes.