This issue reviews the assembly of a basic circuit with an LED and push button. We compare the use of a push-button and a switch in the same circuit. The lesson emphasizes how closed circuits work and the flow of current through a circuit. The circuit uses a resistor to limit the amount of current flowing through the LED. The resistor demonstrates how we limit the flow of current through a circuit. Students understand that current is something that flows through a circuit event if we can’t see it flowing.