In October 1962, Nick Holonyak and colleagues at General Electric built the first practical light-emitting diode, or LED, that could emit visible light. Semiconductor LEDs are now a part of uncountable electronic devices. They've gone from being just a glowing indicator light on a control panel to being a source of room lighting, with many improvements in color, size, efficiency, and cost. Holonyak discusses the invention, and his work since then.