The speed of light is the universal speed limit, so naturally, optical technologies appeal when trying to construct speedy computational devices. Fiber optics let us shoot data to and fro at top speed, but for the time being our CPUs still make their calculations using electronic transistors. Good news is, researchers from Purdue University have built an optical transistor out of silicon that can propagate logic signals -- meaning it can serve as an optical switch and push enough photons to drive two other transistors. It's constructed of a microring resonator situated next to one optical line that transmits the signal, and a second that heats the microring to change its resonant frequency. The microring then resonates at a specific frequency to interact with the light in the signal line in such a way that its output is drastically reduced and essentially shut off. Presto, an optical transistor is born. Before dreams of superfast photonic computers start dancing in your head, however, just know they won't be showing up anytime soon -- the power consumption of such transistors is far beyond their electronic counterparts due to the energy inefficient lasers that power them.