Microwaves both documents and celebrates the Renaissance that we are now living through in microwave technology and applications. Microwaves’ unique spectral region spans a wavelength range of more than six decades, from 30 meters to 30 micrometers (MHz-THz). Today, microwave devices are ubiquitous. They are literally the glue that binds our social networks. They crop up in every corner of technology. They cross disciplines as diverse as communications and cooking, and appear in devices and instruments from the millimeter-square silicon chip to the hundred-meter-square tokamak, at power levels from nanowatts to gigawatts. They have been undergoing continuous development for almost one-and-one half centuries, and now they infiltrate almost every aspect of our lives – unseen, unheard, often unnoticed. No longer!