Wireless power transfer (WPT) is an old subject, introduced for the first time by Nikola Tesla in the twentieth century [1]. His patent proposal was based on the magnetic resonance of two coils to distribute large amounts of energy to distant places of consumption. The subject returned to the mainstream in the last decade due to the exponential growth in the number of electronic devices. Currently, the main goal is to achieve ubiquity of WPT with the consolidation of the Internet of Things (IoT). How to supply the energy necessary to operate this huge network of gadgets is still a problem waiting for a solution. Three main aspects must be considered when outlining the powering strategy of those forthcoming technologies: small physical volume, high energy efficiency, and compatible aesthetics. Other emerging topics have similar requirements, such as battery-less medical implanted devices, remote contactless, and radio frequency identification (RFID), to mention a few.