During the last few decades, implantable medical devices (IMDs) changed the landscape of modern medicine. Combining many technologies and employing smart medical devices within the human body, they allowed a continuous and automatic management of numerous health issues, such as pacemakers and implantable cardiac defibrillators, cochlear implants, bladder controllers, endoscopic capsules, nerve stimulators, lab‐on‐a‐chip, and artificial retinal prosthesis. Due to their continuously increasing potential, IMDs are getting more complex, thus requiring more energy to operate. Most of these advanced implantable devices are extracorporeally powered or battery charged through wireless power transfer (WPT) mechanisms. Following the basic principle of IMD power supplies, we introduce various power transfer techniques, and then focus on the inductive links and various methods to maximize the energy transferred to implantable devices and the calibration methods of these WPT techniques.