The water management role of a microporous layer (MPL) in a polymer electrolyte membrane fuel cell (PEMFC) is demonstrated experimentally by visualizing the drainage behaviors of a non-wetting fluid through multiple porous layers. An intermediate layer inserted between a fine layer and a coarse layer is observed to reduce the number of (the non-wetting fluid) breakthrough sites towards the coarse layer by merging many transport paths. Then, the reduced number of the breakthrough sites decreases the non-wetting fluid saturation in the coarse layer by minimizing capillary fingering process. These results clearly demonstrate the water management role of an MPL: An MPL reduces the liquid water breakthrough into a gas diffusion layer (GDL) by merging many paths from a catalyst layer (CL), and thereby reduces the liquid water saturation in the GDL. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.