Each year, the size of transistors shrinks, thereby improving performance. Yet transistors must be big enough to allow electrons to pass through. Preparing for an inevitable impasse, Toshiba recently demonstrated a transistor that can turn on and off based on the movement of a single electron. Unlike other experimental quantum-level transistors, the device can operate at room temperature. It's also the first successful hybrid circuit, mixing single-electron transistors with traditional metal-oxide transistors, which are required to boost the weak quantum-level signal. Chips based on the circuit should offer blazing performance and low power consumption. Before building a full-fledged processor, researchers face challenges such as finding a way to protect the chip from the disrupting effects of stray electromagnetic fields, electrical discharges and physical movement. Hybrid chips should be available commercially by 2010. -C. Conti