Two-stage valve comprising: - a first stage constituted by a main valve body provided with at least one fluid inlet duct for inletting fluid into the main valve and with at least one fluid outlet duct for outletting fluid out from the main valve, between the fluid inlet duct of the main valve and the fluid outlet duct of the main valve being interposed at least one shutter element of the main valve, configured to put selectively in fluid communication said fluid inlet duct of the main valve with said fluid outlet duct of the main valve; and - a second stage constituted by a pilot valve body provided with at least one fluid inlet duct for inletting fluid into the pilot valve and with at least one fluid outlet duct for outletting fluid out from the pilot valve, wherein said at least one fluid inlet duct of the pilot valve is put in fluid communication with the fluid inlet duct of the main valve, whereas said at least one fluid outlet duct of the pilot valve is put in fluid communication with the fluid outlet duct of the main valve, and wherein between said at least one fluid inlet duct of the pilot valve and said at least one fluid outlet duct of the pilot valve is interposed at least one shutter element of the pilot valve, configured to put selectively in fluid communication said at least one fluid inlet duct of the pilot valve with said at least one fluid outlet duct of the pilot valve, so that the opening of said at least one shutter element of the pilot valve generates a fluid flow passing through said at least one fluid inlet duct of the pilot valve and said at least one fluid outlet duct of the pilot valve, the pressure of said fluid flow generating the opening of the shutter element of the main valve, wherein said at least one shutter element of the pilot valve is actuated by an actuator device comprising at least one wire made from a shape-memory alloy, said at least one wire being able to apply a force onto said at least one shutter element of the pilot valve as a consequence of a temperature variation determined by the Joule effect by the flow of an electric current through said at least one wire, and wherein said at least one shutter element of the pilot valve consists of a piston movable with rectilinear motion, the two-stage valve being characterised in that said piston is kept in a normally closed condition by a thruster element belonging to the actuator device and actuated by an elastic element, the force exerted by said at least one wire made from a shape-memory alloy on said at least one shutter element of the pilot valve allowing the elastic force generated by said elastic element to be overcome, so as to take said at least one shutter element of the pilot valve into a partially or a totally open condition. - a first stage constituted by a main valve body provided with at least one fluid inlet duct for inletting fluid into the main valve and with at least one fluid outlet duct for outletting fluid out from the main valve, between the fluid inlet duct of the main valve and the fluid outlet duct of the main valve being interposed at least one shutter element of the main valve, configured to put selectively in fluid communication said fluid inlet duct of the main valve with said fluid outlet duct of the main valve; and - a second stage constituted by a pilot valve body provided with at least one fluid inlet duct for inletting fluid into the pilot valve and with at least one fluid outlet duct for outletting fluid out from the pilot valve, wherein said at least one fluid inlet duct of the pilot valve is put in fluid communication with the fluid inlet duct of the main valve, whereas said at least one fluid outlet duct of the pilot valve is put in fluid communication with the fluid outlet duct of the main valve, and wherein between said at least one fluid inlet duct of the pilot valve and said at least one fluid outlet duct of the pilot valve is interposed at least one shutter element of the pilot valve, configured to put selectively in fluid communication said at least one fluid inlet duct of the pilot valve with said at least one fluid outlet duct of the pilot valve, so that the opening of said at least one shutter element of the pilot valve generates a fluid flow passing through said at least one fluid inlet duct of the pilot valve and said at least one fluid outlet duct of the pilot valve, the pressure of said fluid flow generating the opening of the shutter element of the main valve,