The instrument used to prepare caffè at home, the caffettiera, is essentially a small steam machine made of a bottom boiler, a central filter which contains the coffee grounds, and an upper cup. In the traditional Moka, water is put in the boiler and the resulting boiling water passes through the coffee grounds, then reaches the cup. The Neapolitan caffettiera operates somewhat differently, and needs to be turned upside down when the drink is ready.