TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Cover: The inside of the container is at a higher pressure than the outside. The opening is a hole or, preferably a small tube, particularly of aluminum or silver, that is wide enough to allow insertion of a probe, sensor, pipette, pH electrode etc. The cover may have dividing elements that separate the container into gas and/or liquid tight compartments, and also a sterile gas lead connected to one, many or all of the containers. Particularly the gas lead is integrated into the cover or the cover includes an adjacent gas-distribution structure, with the channels of this structure being within the cover. The gas inlet is optionally connected to a gas supply, optionally through a sterile filter and/or air moisturizer. The cover includes at least one flat layer or plate that can close the opening of at least one container.Preferred Device: This includes a stirrer for the culture suspension, arranged so that the flow rate along a flow line or track around the stirrer axis can be varied, in space and/or time, particularly so that the suspension is forced from the surfcae to the base, optionally also with a component axial to the axis of stirring. The inner wall that retains the culture has, below, at and/or above the rotational plane of the stirrer, a shape that is not rotationally symmetric, especially having 4 or more corners. The inner wall has, along the circumference of the stirrer, at least one flow breaker, preferably several equally spaced, positioned above, at and/or below the rotational plane of the stirrer. The minimum spacing between stirrer and flow breaker is 0.05-20, preferably 0.1-3, mm. The container may be a flask, glass or cavity in a microtiter, or other, plate, and the stirrer is positioned and/or driven magnetically; optionally also is mounted on a shaft. The stirrer and flow breakers can be formed as a single piece. Particularly the stirrer includes a peforated base, typically oval, egg-shaped or rectangular, through which liquid can circulate, and is driven at 1-400, preferably at least 1000, rpm. The arrangement of (2) consists of a block having several cavities, functioning themselves as containers or designed to receive containers. The block includes systems for controlling temperature, driving the magnetic stirred and/or for supplying sterile gas.