Reticular chemistry — the linking of well-defined molecular building blocks by strong bonds into crystalline extended frameworks — has enabled the synthesis of diverse metal–organic frameworks (MOFs) and covalent organic frameworks, in which the pore shape, size and functionality can be tailored towards specific applications. Structural design methodologies are based on three main requisites: building blocks, targeted nets and isoreticular chemistry. In this Review, we highlight the well-developed and cutting-edge methodologies in reticular chemistry for the structural design and discovery of periodic solids. We illustrate the diversity of building blocks and delineate the suitable blueprint nets — namely, edge-transitive nets — for the design of MOFs. These edge-transitive nets are classified into three categories to help rationalize existing MOFs and to provide guidelines for the design of new structures. Two emerging topological concepts, namely, the merged-net approach and net-coded building units, are highlighted for their potential in synthesizing intricate or multi-component MOFs. We also consider isoreticular design strategies for the modification, expansion and contraction of building blocks, and identify challenges and opportunities in the assembly of increasingly intricate frameworks.