I made this circuit sometime back and I am still unsure of how it works. I saw a 2-LED version from Talking Electronics and tried this 3-LED version. All the explanations I found online are confusing. Apparently, one of the capacitors drains charge from its side of the circuit and switches off its transistor. The resistor connected to it ensures that it accumulates charge slowly. While this happens, it turns on the transistor on another side of the circuit. When that transistor turns on, the its LED lights up. When the first capacitor is fully charged, it stops supplying charge to this transistor and its LED turns off. By this time, its capacitor is accumulating charge and turning on another transistor and the LED connected to it turns on. This repeats one after another. At least, that is my understanding. It could be wrong. The flip-flop delay is controlled by the capacitor and resistor values. The voltage supplied to the circuit should be just enough to light up one LED.