Programming living cells with synthetic gene circuits to perform desired tasks has been a major theme in the growing field of synthetic biology. However, gene circuit engineering currently lacks the same predictability and reliability as seen in other mature engineering disciplines. This book introduces the design methodology for engineering novel modular and orthogonal genetic logic devices, and the predictable functional assembly of modular biological components into customisable biological circuits. Various genetic logic devices, including AND, NOT and NAND gates, were constructed in Escherichia coli bacteria to achieve customised cellular computing and sensing. An effective parts-based engineering approach is presented for assembling individual biological parts into functional circuits using engineered ‘in-context’ characterised modules aided by modelling. The book is a pioneering work in the field, and should be useful for engineers who would like to engineer synthetic biological systems for human desired purposes and for biologists who are interested in the design principles of natural biological circuits.