Major technological shifts in solid-state device technology have typically been associated with improvements in device energy efficiency. This was true in the transition from vacuum tubes to bipolar transistors in the 1950s, and then again from bipolar transistors to MOSFETs in the 1970s. The next technological revolution will similarly stem from an improvement in energy efficiency at the device or at the circuit level. This lecture will explore ways in which new materials and transistors can extend the performance of electronic systems.