This one is the good old two transistor multivibtrator (pictured), where you can watch voltages change and blobs of current run around – obviously in the opposite direction to any electrons that might be making that current work 🙂

While I can find a way to observe the base voltages go negative (mouse-hover over component legs for voltages and wires for current), I can;t find a way to get a plot of base voltage.

Neat