NOVELTY - The valve (100) has a valve opening (125), where a valve plate (116) is arranged to seal the valve opening in a closed state by compressing a sealing structure. The sealing structure includes an uncompressed dimension in a compression direction of less than 100 micro meter. The valve plate compresses the sealing structure by more than 10 percent to a compressed dimension in a compression direction when external pressure is not applied to the valve in a closed state. The sealing structure comprises silicon, caoutchouc or PTFE as a sealing material.    USE - Valve i.e. micro check valve, for a micro peristaltic pump used in medical applications and fuel cell applications.    ADVANTAGE - The value ensures that dead volume can be reduced due to reduced dimension of the sealing structure in a compression direction. The valve plate and the valve opening are formed in thin layers or foils arranged with each other at a top part, so that the dimension of the sealing structure in the compression direction can be reduced, and height of a layer structure comprising the valve can be reduced. The use of elastic and highly-elastic sealing materials such as silicone or caoutchouc, improves sealing characteristics of micro check valves. The application of thin sealing structures of height less than 100 micro meter in an uncompressed state and sufficient elasticity decreases the extent to which the spring elements are deflected in a closed state of the valve, thus reducing material fatigue and fatigue of restoring force of a spring element. The valve ensures that metal foils with a height or thickness less than 500 micro meter can be provided at low costs and structuring of metal foils or layers for forming the holes, plate structures or other structures can be performed using laser ablation or etching processes in a cost effective manner.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a micro pump comprising a layer structure    (2) a method for producing a valve.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a micro check valve in a closed state.    Micro check valve (100)    Valve plate (116)    Spring element (117)    Surfaces (122, 124)    Valve opening (125)