The quest for functional materials targeted at specific applications is ever increasing as societal needs and demands mount with advancing technology. One class of inorganic-organic hybrid materials, metal-organic materials (MOMs), has burgeoned in recent years due, in part, to effective design strategies (e.g., reticular chemistry) for their synthesis and their inherent (and readily interchangeable) hybrid, highly functional character. The molecular building block (MBB) approach introduces the ability to generate rigid and directional building blocks, mostly in situ, for the construction of MOMs having specific underlying networks and/or targeted functions/properties. Various MBBs can be targeted and utilized in the assembly of functional MOMs: (i) single-metal-ion-based MBBs, which promote rational construction, by forcing rigidity and directionality through control of the metal coordination sphere and judicious selection of suitable heterofunctional (N-, O-coordination) organic ligands, of porous MOMs with extralarge cavities, including zeolitelike metal-organic frameworks (ZMOFs); (ii) multinuclear metal-cluster-based MBBs, where, for example, simple metal-carboxylate clusters possess multiple metal-oxygen coordination bonds that result in the generation of rigid nodes with fixed geometry that, when combined with organic ligands of specific geometry, lead to the construction of desired MOMs; and (iii) supermolecular building blocks (SBBs), which involve enhanced built-in directional and structural information (e.g., high degree of symmetry and connectivity) compared to simple MBBs and allow the construction of high-connectivity nets (e.g., rht-MOFs). The MBB approach and associated strategies, as well as physical properties of some corresponding MOMs, are presented.