A valve for switching of media, such as liquids or gases, is opened, closed or put into an intermediate state by at least one actuator produced from a shape memory alloy. The at least one actuator, as a function of whether electricity is applied to it, acts on at least one valve ball or a valve plunger accommodated in a core element, so that the through-flow of a medium through a fluid part below the core element, with a media-tight membrane interposed between, is opened, interrupted or partially opened in regulated or controlled manner. The core element is produced from a mechanically rigid and thermally well-conductive material, has electrical conductor tracks for electrical connection of the actuator to a supply of electricity on the top side, as well as multiple threaded through-holes for underside connection with the fluid part and the membrane and/or for top-side connection with the actuator.