Book excerpt: This first book devoted to this hot field of science covers materials with bimodal, trimodal and multimodal pore size, with an emphasis on the successful design, synthesis and characterization of all kinds of hierarchically porous materials using different synthesis strategies. It details formation mechanisms related to different synthesis strategies while also introducing natural phenomena of hierarchy and perspectives of hierarchical science in polymers, physics, engineering, biology and life science. Examples are given to illustrate how to design an optimal hierarchically porous material for specific applications ranging from catalysis and separation to biomedicine, photonics, and energy conversion and storage. With individual chapters written by leading experts, this is the authoritative treatment, serving as an essential reference for researchers and beginners alike.