This book is about materials which are used for their electrical and magnetic properties rather than their mechanical properties. Assuming a working knowledge of basic scientific, technological and material ideas, many of the consequences of the behaviour of electrons within the material are explained. Exploiting the electronic properties in a wide range of products calls for careful manipulation of the materials' structures at atomic and microstructural levels. Modern circuit-building technologies (printed, hybrid and integrated) are discussed together with ways of providing circuit components at each level of scale. Electronic and magnetic transducers in measurement and in the control of several systems are examined. The book looks at technologically important magnetic effects, from the atomic scale up to complete magnetic components such as tranformer cores and magnetic memory systems for computers. It investigates visual display technologies with emphasis on the specifications needed to meet the demands of the human viewer. An appreciation of semiconductor memory systems is given from the standpoint of how appropriate fabrication technology can improve performance. Finally these topics are brought into an entreprenurial context - the real world - using the drive into new superconductors as a study of interplay of manufacture and marketing of innovative products.