There is a brief review of computer architecture, binary math, and digital logic that you can skip, if you are familiar with these topics.
The evolution of the 8-bit processors is a history of the advance of semiconductor technology from the first transistors, to the breakthrough of multiple transistors on a chip, the integrated circuit. A lot of this happened when the "Silicon Valley" of northern California was mostly known for its citrus crops. The tools that made all this happen were large mainframe computers with vacuum tube technology, punched card input, and memory drums with the staggering capacity of a thousand words. The growth of the integrated circuit shows what Gordon Moore observed was an exponential growth law: the complexity increased about every 18 months. Naturally, this growth rate is not sustainable forever. But, in the age of multi-core 64-bit microprocessor systems on a chip, so far, so good.