The Large Area Telescope (LAT) on board Fermi, the most sensitive ever 
launched gamma-ray telescope, has been gathering high-quality data for 
over 7 years. Beside detecting 3000 point-like sources it has shed light on 
the origin of the extragalactic gamma-ray background, the extragalactic 
background light and the strength of the intergalactic magnetic field. 
In this talk I will review all these aspects with a focus on the regimes 
that the LAT can explore in the near future.