Biofilm growth relies on the transport of solubilized nutrients and waste largely by diffusion, but the mechanism of transport over large distances, when diffusion is limited, has been unclear. A recent study reports the discovery of an integrated network of channels that transport liquid through wild-type Bacillus subtilis biofilms. Because the flow of liquid is strongly influenced by biofilm architecture, the impact of characteristic macroscopic wrinkles in mature B. subtilis biofilms was examined using microscopy. In contrast to flow in flat regions of the biofilm, liquid flowed rapidly into the spaces directly below the wrinkles and followed a network of interconnected channels with well-defined structures. Furthermore, spatial variation in the degree of evaporation from the surface of biofilms was found to be responsible for driving the flow of liquid in the networks. As the biofilm aged, the channels were maintained, although their structure changed, suggesting that they are physiologically relevant during the biofilm life cycle.