One of the advantages of optogenetics is that this technology allows scientists to focus on one particular type of neuron without affecting other types of neurons in the same area of cortex. Probes that deliver electricity to the brain can manipulate neurons, but they cannot target individual kinds of cell. 

Each probe is just 150 microns across, a little thicker than a human hair, and thin enough so that the device can be implanted at any depth in the cortex without damaging it. The brain lacks pain receptors, so the implants do not cause any discomfort to the brain itself. As in the earlier model, several light-emitting ports are located along the length of each probe. Scientists can illuminate and change the color of each light port independently from the others.