The invention relates to a valve (1), comprising a valve housing (4) and a closing body (3) arranged in the valve housing (4) in such a way that the closing body can be moved longitudinally, wherein at least one inlet channel (5) and at least one outlet channel (6) are arranged in the valve housing (4). The closing body (3) interacts with a valve seat (8) formed on the valve housing (4) by means of the longitudinal motion of the closing body and thereby opens and closes at least one hydraulic connection between the at least one inlet channel (5) and the at least one outlet channel (6). The closing body (3) can be driven by means of a metal-bellows/piston unit (2), wherein the metal-bellows/piston unit (2) has a variable-length metal bellows (20) and a variable-volume working chamber (23) and wherein the metal bellows (20) bounds the working chamber (23) in a sealing manner.