A microprocessor constitutes the heart and soul of a personal computer. Indeed, the quality of a personal computer is determined largely by the type of microprocessor that is included within its circuitry. Since the microcomputer revolution began in the late 1970s, these special chips have gone through a series of improvements and modifications. Today's personal computers are much faster and more efficient than the personal computers of 10 or 15 years ago. We are witnessing developments that were unthinkable in the areas of hardware and software. Graphics, multi-media, and desktop publishing are just a few of the fields that have been made possible due to superior hardware capabilities. While the developments we are seeing are amazing, we are also finding uses for these new machines as fast as they are being developed. This article explores the evolution of microprocessors. It details the changes in data path size, miniaturization, instruction sets, use of alternative materials, and other innovations. It does this in a way that is intended to be understandable for the average classroom teacher and will allow teachers to see the fundamental differences that exist between various computer platforms and models within those platforms. Data about the different models of processors and a glossary of related terms are appended. (Contains 8 references.) (Author/ALF)