Integrated circuits have become smaller, cheaper, and more reliable and certainly have revolutionized the world of electronics. Integrated circuits are used in almost all electronic devices and systems, many of which, such as the Internet, computers, and mobile phones, have become essential parts of modern life and have changed the way we live. Quantum-dot cellular automata (QCA) provides a revolutionary approach to computing with device-to-device interactions. The design of a QCA circuit is radically different from a conventional digital design due to its unique characteristics at both the physical level and logic level. Research on both circuit architecture and device design is required for a profound understanding of QCA nanotechnologies. This detailed reference presents practical design aspects of QCA with an emphasis on developing real-world implementations.