This chapter prepares a foundation for the rest of the chapters on micro electric discharge machining (EDM). The general trend of miniaturization is described with a discussion on different categories of micromanufacturing processes. Evolution of EDM is reported in terms of process improvement and machine structure. The difference between macro EDM and micro EDM is put forward in terms of process parameters as well as different components of the machine. Different variants of micro EDM is introduced, which are discussed in more detail later in separate chapters. The chapter is concluded with the advantages and conclusion of micro EDM.