Book excerpt: This book provides comprehensive coverage of different aspects of low-power circuit synthesis for IoT applications at various levels of the design hierarchy, starting from the layout level to the system level. For a seamless understanding of the subject, the basics of MOS circuits have been introduced at the transistor, gate and circuit level, followed by various low-power design methodologies, such as supply voltage scaling, switched capacitance minimization techniques, and leakage power minimization approaches. The contents of this book are useful to students, researchers, as well as practicing engineers. Low-power architectures refer to the latest development in computer microchips which are created by integrating hundreds of thousands of transistors on one chip for different IoT applications. Emerging research in this area has the potential to uncover further applications for IoT in addition to system advancements.