In the Tinkering Studio at the Exploratorium in San Francisco, a group of young people is making tiaras–light-up tiaras. Using copper wire, a soldering iron, batteries and LED lights, they use trial and error to build the kind of design they want. In the process, they start to figure something out. If you want all your lights to glow, you have to create a parallel circuit. A series circuit will not provide enough voltage.