There is disclosed a heat exchanger comprising: a plurality of first fluid channels, a plurality of conduits for interconnecting the first fluid channels, a plurality of second fluid channels, a plurality of conduits for interconnecting the second fluid channels, wherein the heat exchanger is configured as a plurality of repeating units, each repeating unit comprising: a base plate comprising a first opening, and a first conduit extending from the plate, the shape of the opening corresponding to the shape of the conduit.