The evolution of star-forming galaxies is a history of continuous accretion of fresh gas from the surrounding environment. The main evidence of this accretion is indirect coming from the estimate of depletion times and the chemical composition of gas and stars in our Galaxy. In recent years, observational evidence has been accumulating that star-forming galaxies are surrounded by massive gaseous halos containing a large amount of multiphase gas. To understand how this gas falls and accretes to feed star formation we must understand the complex physics of the interphase between the discs and the halo. After a review of the current observations, I present theoretical work and hydrodynamical simulations supporting the idea that gas accretion comes from the condensation of the galactic hot halo triggered by supernova feedback. I discuss some key predictions of this model and its consequences for the evolution of star-forming galaxies.