Until now, the use of optogenetic techniques to depolarize neurons in awake behaving animals has required the animal to wear a head-mounted device to deliver a light source. Now, a miniaturized wireless device that is powered and controlled by radio waves has been developed and can be implanted subcutaneously. The device delivers enough light to activate channelrhodopsins in the central or peripheral nervous systems, thus enabling neuronal depolarization while observing less restricted behaviour than previously possible.