Summary: This is the world's slimmest addressable RGB LED matrix that can be made with 5050 WS2812b Individually addresable NeoPixel LEDs. Why? Because on this PCB the LEDs are not actually on top of the PCB, rather it's inside the PCB.Luckily the height of the LEDs are the same 1.6mm, as most of the commonly used PCB thickness. That makes it possible to have a completely flat surface as well. I conduct this experiment to see how far we can push the limits of modern design tools and techniques.