The manipulation of electron spin offers new dimensions for basic and applied research, and the potential for new capabilities for electronics technology. Device structures that are based on ferromagnetic materials and utilize spin-dependent transport have had a large technological impact on the magnetic recording industry, and are poised to impact integrated, digital electronics. The field of Spintronics is presented in the context of basic physical principles of carrier spin injection, transport and relaxation. Device families, which typically incorporate one or more magnetic component, are described. These include all-metal structures such as spin valves and magnetic tunnel junctions, hybrid ferromagnet - semiconductor devices that operate using magnetic fringe fields, and semiconductor based spin injection devices. Applications are focused on high density, high performance information processing and range from nonvolatile random access memory and reprogrammable logic to "system on a chip" integration of memory and logic.