In order to be able to introduce fluid components extraneous to the system into a modular microfluidic system comprising modules arranged alongside one another which can be connected to one another with fluid connection by connecting parts comprising connecting channels with short connecting paths and good temperature controllability, a module with the following features is provided: the module has a plate-shaped microfluidic part which comprises a fluid channel system and on whose top side, in edge regions to the potentially adjacent modules of the microfluidic system has fluid connections, the fluidic connection to adjacent modules being establishable by means of the connecting parts adjacent in edge regions on the upper side, below the microfluidic part is arranged an insulation vessel which can be filled and flowed through by a temperature control fluid and is concluded at the to by the microfluidic part which serves as a lid.