A heat exchanger comprises: a plurality of first fluid channels defining a flow path for a first fluid; a first fractal channel for conveying the first fluid to the plurality of first fluid channels; and a second fractal channel for conveying the first fluid from the plurality of first fluid channels; wherein the first fractal channel and the second fractal channel each comprises at least one divergence point along its length where a parent channel splits into a plurality of sub-channels which diverge away from each other, and wherein one or each of the first fractal channel and the second fractal channel defines one or more through-channels for a second fluid to pass through the respective fractal channel, each through-channel extending from a parent channel side of a divergence point and emerging between the corresponding sub-channels on a sub-channel side of the divergence point.