"Granular ferromagnets getting richer and simpler":
Granular metals and granular ferromagnets in particular are common and popular materials studied by many for many years. Nevertheless, much of phenomena remain poorly understood and some important properties are, surprisingly, unknown. I shall present our new data on Hall effect in granular ferromagnets across the metal-insulator transition that triggered revision of known effects and ideas like giant Hall effect, quantum corrections to conductivity, percolation, quantum percolation, and correlation between Hall effect and resistivity in granular media.