A new solution for enhancing interfacial adhesion between the hydrocarbon (HC) membrane and a perfluorinated catalyst layer (CL) in polymer electrolyte fuel cells (PEMFCs) is successfully demonstrated by J.-K. Park, H.-T. Kim, and co-workers on page 2974. This is realized by the intrusion of micrometer-sized pillars fabricated on the HC membrane into the perfluorinated CL, forming an interlocking interface, like Lego blocks. Owing to a higher expansion with hydration for the HC membrane than for the perfluorinated CL, a strong normal force occurs at the interface of the pillars and the holes, resulting in an eight-fold increase of the interfacial bonding strength.