This experiment demonstrates how heat affects components - in particular, the LED. One heats the LED with a soldering iron for a while with a copper aligator clip (which diverts heat from the LED, thus preventing it from damage). After you remove it and just use the soldering iron on its own, it's luminosity slowly decreases in intensity for a period of time before it burns out due to excessive heat.
OK, I have a little confession to make, I failed this experiment, the LED only got slightly dim after 5 minutes of my soldering iron at 450°C so I gave up!
The stop watch indicates how long the iron had been applied to the LED and the iron station shows the temperature the iron was at.