Although you could wire up eight LEDs each with a resistor to an Arduino pin (like we did for an RGB LED in Lesson 2) you would rapidly start to run out of pins on your Arduino. If you don't have a lot of stuff connected to your 'duino it's OK to do so - but often times we want buttons, sensors, servos, etc and before you know it you've got no pins left. So, instead of doing that, you are going to use a chip called the 74HC595 Serial to Parallel Converter. This chip has eight outputs (perfect) and three inputs that you use to feed data into it a bit at a time.
This chip makes it a little slower to drive the LEDs (you can only change the LEDs about 500,000 times a second instead of 8,000,000 a second) but it's still really really fast, way faster than humans can detect, so it's worth it!
