Modern Vintage Gamer has just released a video demonstrating how the graphics worked in the Nintendo DS handheld console. It was impressive to see how both 2D and 3D graphics could be used together to create very detailed looking games, even in such a small resolution.
If this is your first time watching an MVG “how do the graphics work” video, I suggest going back and starting with the video about the original Game Boy, then GBA before watching this one. You definitely don’t have to watch those to understand this one, however it might add some perspective seeing the evolution of Nintendo handhelds.