A CPU (central processing unit) is basically the “brain” of a computer. It takes instructions, moves data, and coordinates everything from apps to operating systems. What makes this possible are transistors—tiny electronic switches that turn on and off billions of times per second. Modern CPUs pack tens of billions of these transistors into an area smaller than your fingernail. So how do we actually build something this small? The process is called photolithography. Think of it like printing, but instead of ink, we’re using light and chemicals to etch patterns into silicon wafers. Layers of these patterns stack up to create intricate circuits, where each transistor is just a few nanometers wide—smaller than a single virus particle. The architecture of a CPU defines how all those transistors are arranged—how data flows, how instructions are executed, and how performance and efficiency balance out. From pipelines and caches to multi-core designs, CPU architecture is about squeezing the...