“When Brent Williams got to RadioShack that day in the spring of 2012, he knew exactly what he was looking for: a variable resistor, a current regulator, a circuit board, and a 9-volt battery. The total came to around $20 … [later] he snapped the battery into place, turned a small dial, and sent an electric current into his brain.” Wired’s Greg Miller takes you inside the strange new world of DIY brain stimulation. (The most shocking part of this story is that someone still shops at RadioShack.)