The invention discloses a cover (4) for sealing a container (1) and preferably containers (W<1>) for a well plate (W). The cover is comprised of at least a top layer (2) and a bottom layer (3) structured in a way to form a recloseable aperture. Preferably, 5 each of the layers (2, 3) comprise a recloseable aperture structured as flap, damper, baffle or butterfly valve respectively, wherein the recloseable apertures are arranged on top of each other. In a preferred embodiment of the invention a third moveable layer (9) is arranged between the top and the bottom layer (2, 3). By moving the middle layer (9), the aperture in the cover (4) can be closed. |