Two and a half years ago, a team of researchers led by groups at MIT, the University of California at Berkeley, and Boston University announced a milestone: the fabrication of a working microprocessor, built using only existing manufacturing processes, that integrated electronic and optical components on the same chip. The electro-optical researchers’ approach required that the chip’s electrical components be built from the same layer of silicon as its optical components. That meant relying on an older chip technology in which the silicon layers for the electronics were thick enough for optics. A team of 18 researchers, led by the same MIT, Berkeley, and BU groups, reports another breakthrough: a technique for assembling on-chip optics and electronic separately, which enables the use of more modern transistor technologies. Again, the technique requires only existing manufacturing processes.