Book excerpt: Nucleic acids have structurally evolved over billions of years to effectively store and transfer genetic information. In the 1980s, Nadrian Seeman’s idea of constructing a 3D lattice from DNA led to utilizing DNA as nanomolecular building blocks to create emergent molecular systems and nanomaterial objects. This bottom-up approach to construct nanoscale architectures with DNA marked the beginning of a new field, DNA nanotechnology, contributing significantly to the broad area of nanoscience and nanotechnology. The molecular architectonics of small "designer" molecules and short DNA sequences through complementary binding interaction engenders well-defined functional nanoarchitectures with realistic applications in areas ranging from biology to materials science and is termed "DNA nanoarchitectonics." This book discusses novel approaches adapted by leading researchers from all over the world to create functional nucleic acid molecular systems and nanoarchitectures. Individual chapters contributed by active practitioners provide fundamental and advanced knowledge emanated from their own and others’ work. Each chapter includes numerous illustrations, historical perspectives, case studies and practical examples, critical discussions, and future prospects. This book can serve as a practical handbook or as a textbook for advanced undergraduate- and graduate-level students of nanotechnology and DNA nanotechnology, supramolecular chemistry, and nanoarchitectonics and researchers working on macromolecular science, nanotechnology, chemistry, biology, and medicine, especially those with an interest in sensors, biosensors, nanoswitches and nanodevices, diagnostics, drug delivery, and therapeutics.