Schematic for a simple 3x3 LED Cube using the Arduino Nano.
You can find the code for the cube here.
This uses 9 IO pins sourcing current to control the 9 LEDs on each plane, and 3 IO pins sinking the plane's current to control which layer is active, therefore it uses the LEDCubeXZOutYIn class. (IO pins source/output current to the XZ plane and sink/"input" current to the Y layers) If you would like to change the wiring, refer to the instructions in the Nano-3x3-LED-Cube repository.
The schematic was designed in KiCad.