How non-invasive brain stimulation techniques might work, and how we have started to use them in stroke survivors. Non-invasive brain stimulation has been around for thousands of years - from the use of electric fish in Ancient Greece to cure headaches, to the modern use of very small electric currents passed through the brain via two electrodes placed on the scalp. Today, we use stimulation to modulate on-going brain activity, with the ultimate aim of improving hand use after stroke. Here I will discuss a little about how these techniques might work, and how we have started to use them in stroke survivors.