The first chapter of the book deals with the evolution of silicon photonics since its inception in the mid-1980s. During the 1990s the focus was on the waveguides. Silicon optical modulators as transceivers rely on carrier injection, accumulation, and depletion for changing the refractive index in a waveguide as the basic telecommunication component. The research trends are for smaller waveguides to reduce power consumption and real estate. In addition, the chapter discusses key technological challenges: light sources, power consumption, couplers, packaging, and fiber alignments, not to mention size differences in photonics and electronics relevant to plasmonic waveguides.