They look for all the world like any other LED, though embedded in the plastic dome is an integrated circuit to do all that flashing work.

I made this Arduino 8 bit binary led counter as a solution for one member from Arduino forum. He asked if somebody can make a project that displays a decimal number in 8 bit binary format using 8 leds ...

Here is a simple Arduino Camping Light project. In this design, only one push button switch is used to control the light output (from a bunch of white LEDs) between off, dim, medium, and full ...

They look for all the world like any other LED, though embedded in the plastic dome is an integrated circuit to do all that flashing work.