The invention discloses a flow control block for a stack of chromatography column modules, as well as a stack of chromatography modules comprising at least one flow control block. The flow control block is in a first position or configuration capable of connecting two chromatography column modules, or a chromatography column module and an endpiece, in parallel and in a second position or configuration it is capable of connecting two chromatography column modules, or a chromatography column module and an endpiece, in series.