The line follower of GoPiGo3 is composed of six pairs of LED phototransistors. The LED emitter is the right-most part of each pair when you position the sensor in front of you to read the letters. This can be seen in the following photograph, which is a picture of the powered sensor, although you cannot yet see the LED light beams:
Why don't you see them in the picture? Because LEDs emit infrared light, which can't be detected by your eyes; however, it can be revealed by a phone camera (by default, the optics of these cameras do not include infrared filters). So, if, later on, you find that the line follower does not work properly, ...
