The progress in the H2 storage research is illustrated by the concept cluster map shown in Fig. . "Hydrogen storage materials" is the key concept of the map. The concept is commonly used together with "Dehydrogenation", "Hydrogenation", "Dehydrogenation catalysts", and "Hydrides" indicating H2 storage and release via chemisorption. Also "Hydrogen storage materials" frequently cooccurs with "Absorption", "Desorption", "Metal-organic frameworks", and "Carbon nanotubes" which indicate physisorption and common physisorbents. "Microstructure", "Ball Milling", "Nanoparticles", and "Nanostructures" demonstrate current trends in material modification. They often co-occur with "Activation energy", "Surface area", "Pore size", "Pore size distribution", and "Binding energy". Finally, "Fuel cells" and "Secondary batteries" show the way for on-board H2 storage.