Semiconductor makers have supplied ever-more-efficient chips. But performance limits may soon be reached, partly because of the difficulty of making transistors small enough. Conventional transistors switch on or off when a burst of current passes through. As the transistor gets smaller, so does the level of current required. For the smallest of the small, labs have made transistors that switch in response to a single electron-but such nanode-vices have required cryogenic cooling. Now Princeton electrical engineer Stephen Chou has created a single-electron memory that works at room temperature. Manufacture of such devices, however, is several years off, awaiting greater understanding of the chips’ unusual properties.