Hello, I was messing around with a circuit when I accidentally discovered this circuit. The LED stays off until you touch the yellow wire. Can someone explain how this works? I don't understand how just one connection is making the LED light. I know that you can use a transistor to amplify current to pass through skin, but that takes two connections. Can anyone explain how this circuit is working? The resistor is 470 ohms, and the transitor is 2N2222 A338, the input voltage is 9 volts.