You clicked this at the start. Back then it was just a switch.

Now you know that a computer is made of billions of these — each one either on or off. Same idea, just unimaginably smaller and more numerous.

But that's still not the whole story. Switches sitting alone don't compute anything. They have to be wired together into circuits, arranged to make decisions, coordinated billions of times per second.

How that works is what's next.